XCOM: Enemy Unknown Achievement Guide & Road Map

XCOM: Enemy Unknown
XCOM: Enemy Unknown Achievement Guide

Overview:
+ Estimated difficulty: 9/10 for 1100
+ Offline: 54/55 - (1075)
+ Online: 1/55 – (25)
+ Minimum time to 1000: 90+ Hrs
+ Minimum playthroughs needed: 5 playthroughs [DLC: 1 playthrough]
+ Cheats affect achievements: Yes, disables achievements
+ Difficulty affects achievements: Yes
+ Missable achievements: Several (There is no chapter/mission select so many achievements can be missed. The main ones are 'Aint No Cavalry Comin,' 'Edison,' 'All Employees Must Wash Hands,' 'Hunter/Killer,' & 'Skunkworks' [DLC: Rising Dragon, All Aboard]
+ Glitchy achievements: 0
+ Unobtainable achievements: 0

Introduction:
XCOM – Enemy Unknown is a turn based strategy reimagining of the classic game, XCOM UFO defense. After Earth is invaded by unknown alien hostiles, you are given command of the XCOM initiative to try and uncover the invasion plot and drive them out. The game consists of story driven campaign missions with random events and alien invasions happening throughout, and multiplayer that allows you to take on a friend with teams comprising of both human and alien squad members. The campaign will take an average 20 hours to complete and will require a minimum of 5 playthroughs to earn all achievements. While the game itself can be challenging and take several attempts before you find a strategy that works for you, the majority of the achievements are relatively simple and will unlock with little effort as you progress through the story.

The following playthrough strategy is designed to be the quickest way to unlock all achievements while minimising restart/reload times. (Please note, for the most part, the starting locations are interchangeable with playthroughs. It is entirely up to you where you start, as long as you start in a different location each time.

NOTE: The endgame starts when you utilize the Gollop Chamber. If you are trying for certain achievements such as building all foundry items, don't enter the Gollop Chamber or it will prevent all future objectives.

Playthrough 1 –
Difficulty: Easy
Starting Location: North America

The purpose of this playthrough is to familiarise yourself with the game and discover what strategies work best for you. Most of the easier and story related achievements will unlock throughout this playthrough but don’t go out of your way to earn as many as you can until you have a solid understanding of the game and how it works. With the bonus related to having a base in North America being reduced cost and maintenance of aircraft and aircraft weapons, it is a good idea to try and unlock Shooting Stars and Hunter/Killer on this play through. Overall, this playthrough will net you roughly 20-25 of the achievements, most of which will be story related.

DLC: If you are planning on playing the DLC, keep a save from your first play through from immediately prior to entering the Gollop Chamber. When you are ready to play the DLC, download it and then load this pre-Gollop Chamber save. With your advanced end-game ready soldiers, you can stroll through the DLC in about an hour (presuming your first play through is on easy)

Playthrough 2 –
Difficulty: Easy or Normal
Starting Location: South America

Although playing this play through on easy will make some achievements easier, playing on normal may serve as a nice easement to the later play through on classic and impossible difficulty. The main focus of this play through will be to unlock the remaining achievements that don’t require classic or impossible difficulty.Focus on the following achievements during this playthrough: Ain’t No Cavalry Comin, The Hardest Road, As a Scalpel, Edison, Skunkworks & Flight of the Valkyries. With the bonus related to having a base in South America being reduced instant alien autopsies, it is a good idea to try and unlock All employees must wash hands on this play through. At the end of this playthrough you should have at least 40 achievements with a maximum of 43

Playthrough 3 –
Difficulty: Classic
Starting Location: Europe

This playthrough will allow you to focus on the achievements requiring you to be playing on at least classic difficulty. It also serves as an introduction to the harder difficulties but after 2 play throughs already, you should have a decent understanding of how the game plays and already have the majority of achievements, leaving you to focus on the following during this play through: Lone Wolf, Wet Work & Earth First. Also use this play through to mop up any other achievements you may have missed from earlier play through, while Classic difficulty can be tough, trying to unlock achievements on Impossible or Ironman mode can be even tougher. By the end of this play through you should have 46 achievements

Playthrough 4 –
Difficulty: Impossible
Starting Location: Africa

The sole purpose of this playthrough will be to unlock Our Finest Hour. By now you should have a fairly deep understanding of the game and how to overcome the alien invasion. Don’t be afraid to abuse the save game system, even if it means saving after every turn, as one wrong step or unlucky move can screw up everything. By the end of this playthrough you should have 47 achievements

Playthrough 5 –
Difficulty: Classic/Ironman Mode
Starting Location: Asia

In terms of difficulty, playing on Classic should be easier than your Impossible play through but the limit of only one save game file will make this play through the hardest of them all. Again, try and focus only on getting through this play through and don’t try and also work on any achievements you may have missed (unless of course you strongly believe you can.)

Surviving this play through will unlock No Looking Back and A Continental Fellow and give you a total of 49 achievements.

Mulitplayer:
All that’s required in Multiplayer is to win a single match which will unlock Meet New People. Then Kill Them and can be easily boosted if need be.

Mop Up:
If by chance you have missed any achievements, start a new game on easy and mop up the rest.

DLC: Slingshot
The mission as relatively easy and shouldn’t prove too difficult if you have already played through the game at least once. The new maps are very similar to existing ones so again, these shouldn’t confuse or overwhelm you. The council missions can be played through in roughly 30 minutes (depending on how much time you spend on the in between missions). During the first or second month (it will depend on how many missions you are offered in the first month) you will receive a council request. Once this happens you will be given the option of selecting a normal mission, or the DLC mission. From here the three missions will appear one after the other, so you should be all finished by month 3 or 4 (again, depends on the number of missions per month). From here you simply need to keep the new character, Zhang, alive so you can include him in your squad for the final mission.

Conclusion:
XCOM: Enemy Unknown will take time and patience to earn the full 1100. The Slingshot DLC is not difficult but can be time consuming as it requires a full playthrough to unlock the full 100. While the majority of the individual achievements are relatively easy, it can be the overall game that can make the achievements quite difficult, but by finding what strategies work and don’t work, and by having multiple saves files within each game, there shouldn’t be any need to restart an entire play through.

[x360a would like to thank DEG23 & asdfen for this road map]
[x360a would like to thank DEG23 for the DLC addition]

No Looking Back

100
Beat the game in Ironman mode on Classic or Impossible difficulty.
(39)
Although you have the option of playing on either Classic or Impossible difficulty it will be much easier on Classic. Ironman mode means you have only one save file that autosaves after both you and the aliens have had your turn. Although the enemies will be challenging, the main difficulty you will face with this mode is the possibility of making a mistake or wrong decision and being decimated within a few turns, unable to reload a save allowing you to correct this.

You will need to have a solid understanding on how the game plays and what strategies work in each situation. It is highly recommended you attempt a play through on Classic difficulty prior to starting Ironman Mode, as trying to go from Easy or Normal to Classic/Ironman Mode can be overwhelming.

See 'Our Finest Hour' for more on how the difficulties differ.

For a detailed walkthrough/strategy guide on beating Classic/Ironman Mode refer to the Classic/Ironman Mode Walkthrough

You can also find additional gameplay and Ironman mode tips HERE

TIP: (Credit to asdfen) To avoid the ‘one save’ rule you can sign out of your profile before the enemy finishes their turn and rollback a single turn.
Humanity's Savior

30
Beat the game on any difficulty.
(2)
-See ‘Our Finest Hour’
Earth First

60
Beat the game on Classic difficulty.
(4)
-See ‘Our Finest Hour’
Our Finest Hour

90
Beat the game on Impossible difficulty.
(10)
It is highly recommended you have a thorough understanding of how the strategy elements and mechanics of the game work before attempting the game on Impossible. The greatest challenges you will face on Impossible difficulty is the skill and tactics of the aliens and the reduced funding/rewards you earn each month.

The following outlines the difference between each difficulty level:

Easy:
- Initial funding of 175 credits.
- Initial global panic level of 0
- Monthly income increased by 50%
- Begin with an Officer Training School already constructed.
- Begin with 1 satellite in reserve.
- Base begins with 35 power
Normal:
- Initial funding of 175 credits.
- Initial global panic of 0
- Begin with an Officer Training School already constructed.
- Begin with 1 satellite in reserve.
- Base begins with 35 power
Classic:
- Initial funding of 100 credits.
- Initial global panic of 1 per country.
- No Officer Training School at the beginning.
- No extra satellites in the beginning.
- Engineers & Scientists awarded per satellite launched is halved.
- Base begins with 30 power.
- Rise in panic from ignored abduction missions is 2
- Enemies have roughly 10% greater aim/chance to score a critical
- There are more aliens on each map compared to Normal
Impossible:
- Initial funding of 75 credits.
- Initial global panic of 2 per country.
- No Officer Training School at the beginning.
- No extra satellites in the beginning.
- Engineers & Scientists awarded per satellite launched is halved.
- Base begins with 30 power.
- Rise in panic from ignored abduction missions is 3
- Enemies have roughly 10% greater aim/chance to score a critical
- There are more aliens on each map compared to Classic
The key to beating Impossible difficulty is taking your time and knowing the strengths and weaknesses of the aliens and how to counter them with your own soldiers and research projects. Overall there is no one way to beat the game and will depend on your own style and strategies.

Make use of the save system and be sure to have multiple save files going at once. You may find yourself saving after every 2 or 3 turns in case something goes horribly wrong or you just want to give a turn another try. It is also a good idea to make a save at the beginning of each mission (after you land on the ground, not before at the base as the missions will be random) so you can restart if you find yourself employing a strategy that is destined to fail.

NOTE: The percentage outcome of both yours and the alien's shots landing is decided at the start of each turn. So saving directly before taking a shot and reloading if the shot misses is pointless. You need to save at the end of the previous turn to alter the outcome of your shots.

Overall, as long as you take your time, abuse the save system and research/upgrade equipment and satellites regularly, this won’t be overly difficult. Completing the game on Impossible will also unlock 'Earth First'

For a general walkthrough and combat tips/build, refer to the Classic/Ironman Mode Walkthrough as many of these will also apply to Impossible difficulty.
Lone Wolf

20
Clear a UFO crash site with one soldier on Classic or Impossible difficulty.
(23)
This can only be done on a crash site mission and requires a single soldier to kill all aliens on the map. Although it can be completed on ether Classic or Impossible difficulty, it will be much easier on Classic.

The easiest mission to achieve this will be the Small Scout crash sites, as they only have anywhere between 5-8 enemies. Small Scout UFOs will appear early in the game, then randomly towards the end. If you choose to attempt this late in the game, then any or your upgraded soldiers with decent weapons and armor shouldn’t prove too difficult to clear the map on their own.

An alternate strategy is to do this on the very first crash site mission as this is guaranteed to have 4 Sectoids and an outsider. Start a new game, disable the tutorial as this gives you better odds of one soldier being chosen as an Assault. Play through the 2nd mission (abduction) focusing on ranking up your Assault soldier to corporal, (or Squaddie if you missed out on the first mission) and at the end choose the ‘Tactical Sense’ perk. An alternate to the assault class is the sniper utilising the Snap Shot and Headshot ability.

Make sure to save before you deploy to the crash site. (This will mean that every time you reload you receive a different map but this shouldn’t make a big difference to the strategy.) Once on the ground, move up one side of the map slowly. Ideally you want to engage the Sectoids two at a time. With a little luck, 1 of the 2 Sectoids you uncover will mind merge with the other. If this is the case use Run and Gun to move into a position to take out the one doing the mind merging, so that by killing it, you also take out the 2nd Sectoid. If using a sniper, be sure to use headshot on the mind merging Sectoid or take out the Sectoid posing the greatest threat first.

Be sure to reload, and hunker down for 2 turns to recharge your Run and Gun, then repeat for the other 2 Sectoids. Sometimes you won’t be able to get close enough to make use of Run and Gun, so fall back on moving once and using a grenade. Also sometime the Sectoids won’t mind merge, so it is best to fall back and engage them one by one.

Once you have cleared the Sectoids, move up to the UFO and take up position at the front near the door. Do not approach from the side as this can often mean the Outsider will spawn on your second move. Once you are near the door, end your turn, then open the door to make the Outsider spawn. Chances are it will run directly for you. Move inside the UFO giving yourself a clear shot and take out the Outsider. The achievement will unlock on the mission results screen.

This achievement relies heavily on luck so it may take several times to get the right alien placement/strategies before it works in your favor.

NOTE: Some people have reported this achievement to be glitched and will not unlock if you reload a save at any point during the mission. A good strategy is to make a save before leaving the base and reload from that point if you die during the mission.
Bada Boom

10
Kill 50 aliens with explosive weapons.
(2)
This requires you to make a kill using either a grenade or rocket launcher. All classes can carry grenades but only the heavy can use a rocket launcher. This should come naturally as you progress through the game but a good strategy is to use grenades and rockets on weaker enemies like Sectoids and Thin Men, as these tend to group up, or to finish off enemies who have low health. Once the 50th alien is killed the achievement will unlock. This carries across all playthroughs and does not have to be done in a single game.

TIP: Although you can only carry a limited number per mission, grenades are infinite, so it’s a good idea to use up each soldier’s grenade supply each mission.
Welcoming Committee

20
Kill 150 aliens.
(3)
-See ‘Pale Horse’
Pale Horse

50
Kill 500 aliens.
(4)
This will unlock naturally as you progress through the game as the main purpose of most missions is to kill all aliens. Depending on how many side missions you choose to complete, this may take more than one play through.
Shooting Stars

35
Shoot down 40 UFOs.
(13)
To shoot down a UFO you will need a satellite and at least one interceptor. Once a satellite has detected a UFO via scanning the geoscope in mission control, you need to launch an interceptor in the hope of bringing it down. In the beginning of the game this will be fairly easy but as the game progresses, you will need to upgrade not only your interceptors themselves but also their payload to be able to take out the alien’s larger UFOs.

A good strategy is to hanger at least one interceptor per continent with a satellite in orbit. On average you will encounter 1 or 2 UFOs per month so unless you hold off progressing the story, this will take you several playthroughs.

TIP:
Save at the Geoscape then ignore everything & only shoot down UFOs. At game over just reload your save & do it again.
Ain't No Cavalry Comin'

50
Have a soldier survive every mission in a full game.
(28)
This requires a single soldier to not only participate, but also survive every mission in a full game. It is highly recommended this be attempted on easy difficulty but can be achieved on any difficulty.

Unless you are lucky, you will need to make good use of the save game system, reloading if your chosen soldier dies or sustains massive damage. While it may be tempting to keep them towards the back of the map, it is a good idea to use them as the main soldier in your squad, as participating in every mission will allow them to rank up quickly, making them a powerhouse in the later stages of the game.

It is also worth mentioning that your soldier can sustain some damage, as often they will heal in time for the next mission, but this is risky as a mission can pop up at anytime.

Once you complete the final mission and ‘win’ the game, the achievement will unlock.

TIP: When selecting a new game, disable the tutorial as this will give you four soldiers to start with, so you will have a better chance of at least one making it through every mission.
As A Scalpel

25
Earn the "Excellent" rating in every performance category on a terror mission.
(9)
This can be done on any ‘Terror’ mission. The following are the 3 categories and requirements for an ‘excellent’ rating:

- Aliens killed: Kill all aliens on the map
- Operative lost: No squad members can be killed
- Civilians rescued: At least 75% rescued.

The hardest part of this achievement will be rescuing civilians, as the aliens will not waste any time killing them. Unlike some other missions, you will need to play offensively, taking the fight to the aliens quickly. Try and focus most of your attention on killing aliens, instead of rescuing civilians as you can always double back or use a weaker squad member to rescue them later. When engaging aliens, particularly Chryssalids, make sure you focus all your fire on one and kill it, before moving on to the next. In Terror missions, having three wounded aliens is much more dangerous than one enemy at full health.

As long as you have received a rating of ‘excellent’ in all 3 categories, the achievement will unlock during the mission results screen.

TIP: Outfit your squad with ‘assault’ and ‘heavy’ classes as these are better suited to close quarter combat, and (your assault soldiers) can utilise the ‘Run and Gun’ perk. Also to make this achievement easier, outfit a squad using your most experienced soldiers.
Edison

25
In a single game, complete every Research Project.
(22)
Research projects become available after killing aliens, capturing aliens, completing Crash Site/Base missions or by completing prerequisite research. The number of scientists and laboratories constructed will determine the research time of each project. You can increase the overall research speed of projects by adding additional scientists to your staff, by successfully completing missions that offer scientists as rewards, receiving scientists from the council for having satellites in Europe, North America, South America and Africa, and by building additional laboratories. Keep in mind that some research projects will require additional materials, like alien materials or alloys, so try and keep a small supply on hand at all times.

There are a total of 53 projects and all will need to be completed in a single game. You can always check what projects have been researched by selecting the Research Archive in the laboratory menu. The following are the different research projects and how they can be obtained.

Dead Aliens:
- Weapon Fragments (recovered from all alien types)
- Xeno-Biology (recovered from all alien types)
- Alien Materials (recovered from all alien types)
- Berserker Autopsy
- Chryssalid Autopsy
- Cyberdisc Autopsy
- Drone Autopsy
- Ethereal Autopsy
- Floater Autopsy
- Heavy Floater Autopsy
- Muton Autopsy
- Muton Elite Autopsy
- Sectoid Autopsy
- Sectoid Commander Autopsy
- Sectopod Autopsy
- Thin Man Autopsy
Live Aliens:
- Berserker Interrogation
- Ethereal Interrogation
- Floater Interrogation
- Heavy Floater Interrogation
- Muton Interrogation
- Muton Elite Interrogation
- Sectoid Interrogation
- Sectoid Commander Interrogation
- Thin Man Interrogation
UFO/Crash Site/Base missions:
- Alien Nav Computer
- UFO Power Source
- Hyperwave Communication
- Outsider Shard
- Elerium
- Fusion Lance - (Available after shooting down a Large Battleship UFO and completing the crash site mission)
- Guided Fusion Launcher - (Available after shooting down a Large Battleship UFO and completing the crash site mission)
Requires previous research to unlock: (the majority of these will come from interrogation and autopsies)
- Arc Thrower
- New Fighter Craft
- Ethereal Device
- Experimental Warfare
- Carapace Armor
- Titan Armor
- Beam Weapons
- Precision Lasers
- Heavy Lasers
- Light Plasma Rifle
- Plasma Rifle
- Heavy Plasma
- Plasma Sniper
- Alloy Cannon
- Plasma Cannon
- EMP Cannon
- Skeleton Suit
- Plasma Pistol
- Psi Armor
- Ghost Armor
- Archangel Armor
TIP: When going for this achievement, it is a good idea to select your base location as South America, as this will mean all interrogations and autopsies are completed instantly.

Also try and capture each alien as soon as they start to appear on missions, as waiting until later levels can be difficult when attempting to capture several at once. Aliens like Sectoids and Thin Men become less frequent on later missions. When capturing tougher enemies, rely on your veteran soldiers, as you will most likely take a few hits and this will mean instant death for rookies. Also be sure to upgrade your Arc Thrower in the foundry when the upgrade becomes available later in the game. This will mean you can stun an enemy without having to wear down its health first.
All Employees Must Wash Hands...

10
In a single game, complete every Autopsy.
Each autopsy is conducted via the laboratory and will require an alien corpse to do so. Each time an alien is killed, its corpse will be automatically collected at the end of the mission. There are a total of 13 alien autopsies required and all will need to be completed in a single game.
- Berserker Autopsy
- Chryssalid Autopsy
- Cyberdisc Autopsy
- Drone Autopsy
- Ethereal Autopsy
- Floater Autopsy
- Heavy Floater Autopsy
- Muton Autopsy
- Muton Elite Autopsy
- Sectoid Autopsy
- Sectoid Commander Autopsy
- Sectopod Autopsy
- Thin Man Autopsy
TIP: Having a starting base in South America will allow for autopsies to be completed instantly.
Eye in the Sky

5
Launch a Satellite.
This will unlock as you progress through the story. After the 3rd mission you will be instructed to launch a satellite over a country. Select any country and you will be given a time frame for when the satellite will be active. Once the number of days have passed you will receive a notification the satellite is in orbit and the achievement will unlock.
All Together Now

10
Get satellite coverage over every country on one continent.
(1)
To launch a satellite you first need to ensure you have the correct facilities built in your base. Doing this will require you to clear additional space and build access lifts to reach lower levels. You will need to construct additional workshops to allow additional engineers to work in your base. Next you need to build power generators which in turn allows you to build a satellite uplink.

Once this is done select the build satellite option from engineering. Once the satellite has been built visit the situation room to launch it. Repeat the process until there is one satellite over every country in a single continent. Once the last satellite is launched and has moved into position in space, the achievement will unlock.

TIP: Wait until you start in South America (only has 2 countires) before attempting this achievement as you will automatically have a satellite over one country when you choose your starting base, then follow the method above and launch the second satellite over the remaining country.
Hunter/Killer

15
In a single game, shoot down one of each alien craft.
To increase the chances of detecting a UFO, be sure to constantly produce and launch satellites around the globe. Also be sure to have at least one interceptor based at each country with a satellite, (preferably 2 with different armaments). As new armaments become available to research and build, give them priority as they will be the key to bringing down the different types of UFOs. When available, prioritize the Firestorm as these are essential to shooting down the largest UFOs.

The following are the 6 UFO types that need to be shot down in a single game:
- Small Scout (Can be shot down with basic Interceptor)
- Medium Scout (Can be shot down with basic Interceptor but is best to use phoenix cannons)
- Large Scout (Can be shot down with Interceptor but will require laser weapons and Targeting/Agility mods)
- Supply Barge (Will require Firestorm upgrade with Laser or Plasma weapons)
- Abductor (Will require Firestorm upgrade with Plasma, EMP or Fusion Lance weapons)
- Battleship (Will require Firestorm upgrade with Plasma, EMP or Fusion Lance weapons)
NOTE: Be sure to shoot down the smaller UFO's when they first appear, otherwise they will become less frequent the further you progress in the game.

After you have shot the UFO down, the next screen will show you what type of UFO it is. (Bottom left corner)
Man No More

10
Build a suit of powered armor.
There are 3 types of powered armor, Archangel, Ghost and Titan armor. All 3 are researched via the laboratory and built via engineering. You will most likely research these as you progress through the game but they will not be available until later in the game. Once the armor is built, the achievement will unlock.
We Happy Few

10
Complete a mission without losing a soldier.
(4)
This requires all members of your team to survive the mission. They can take damage but cannot die. This is best done on an easier difficulty and towards the beginning of the game as most of the aliens you face will be Sectoids. This can be unlocked as early as the 2nd mission.

TIP: Take it slow and don’t rush. Try and focus on 1 or 2 aliens at a time and don’t spread your team too far apart. If one team member sustains damage, move them towards the back and bring your full health members up.
The Hardest Road

10
Advance one of your soldiers to Colonel rank.
Colonel rank is the highest a soldier can achieve and will require them to be present in most missions. Soldiers rank up by damaging/killing/capturing aliens, performing actions like firing while on overwatch/suppressing, and surviving missions unharmed. Reaching the rank of Colonel will take time and require a single soldier to be present on most missions throughout the game. It’s a good idea to use higher ranked soldiers as the driving force when attacking, as performing more of the actions mentioned above will result in faster promotions. Also remember, when ranking up and choosing perks, choose perks that suit your play style allowing you to utlilise the soldier more effectively.

TIP: It is a good idea to work on this achievement while going for ‘Ain’t no cavalry comin’ because if you use the same soldier on every mission, they will reach colonel easily. You can also buy the 'Wet Work' perk from the Officer Training School for 125 credits that grants soldiers additional experience per kill.
Worth Every Penny

20
Acquire 1000 credits in one month.
You will receive credits on a monthly basis from the council and your monthly income is dependent on how many satellites you have in orbit and how many countries are currently still part of the council. You can earn additional money throughout the month as rewards from completing certain missions, fulfilling council requests, and by selling materials and alien corpses on the grey market.

1000 a month may come naturally, however if you find you are struggling, save your game then start selling most of your equipment/recovered tech on the grey market. Once the achievement unlocks, reload the save.

TIP: Playing on Easy or Normal difficulty will make this achievement easier to unlock, as it will be easier to manage the panic levels and allow for continued full support from the council each month.

Also having a starting base in Africa will increase your monthly council funding by 30%.
Oppenheimer

20
Staff the Research Labs with 80 scientists.
(2)
Additional scientists can be obtained as rewards for completing certain missions, (mainly abduction missions,) monthly rewards for having satellites in Europe, North America, South America and Africa (the more satellites, the more scientists you will receive each month,) and from the occasional council request. Once you have a total of 80 scientists, the achievement will unlock. This will most likely come naturally towards the later stages of the game

TIP: If the achievement does not unlock naturally over the course of the game, start a new game on easy and focus on completing tasks/launching satellites that will net you the most scientists. If given the option between adding scientists or engineers, always choose scientists.
One Gun at a Time

20
Staff the Engineering Department with 80 engineers
Additional engineers can be obtained as rewards for completing certain missions, (mainly abduction missions,) monthly rewards for having satellites in Asia, North America, South America and Africa (the more satellites, the more scientists you will receive each month,) and from the occasional council request. You can also add additional engineers by building additional workshops. Once you have a total of 80 engineers, the achievement will unlock. This will most likely come naturally towards the later stages of the game.

TIP: If the achievement does not unlock naturally over the course of the game, start a new game on easy and focus on completing tasks/launching satellites that will net you the most engineers. If given the option between adding scientists or engineers, always choose engineers.
Skunkworks

20
In a single game, complete every Foundry project.
(6)
Each foundry project will require either money, alien materials, previous research, engineers or a combination of all. There are a total of 18 projects and all will need to be completed in a single game.
- Heavy Weapons Platform
- Alien Grenades
- Improved Medikit
- Improved Arc Thrower
- Advanced Repair
- SHIV Laser
- SHIV Plasma
- SHIV Repair
- SHIV Suppression
- Drone Capture
- Ammo Conservation
- Advanced Flight
- Advanced Construction
- Improved Pistol I
- Improved Pistol II
- Improved Pistol III
- Stealth Satellites
- SCOPE Upgrade
You Have 5 Seconds to Comply

10
Build a S.H.I.V.
(3)
Before you can build a SHIV, you first need to build a foundry. From here you can research heavy weapons platform. Once this is done, proceed to engineering and build the S.H.I.V. Once construction is complete, the achievement will unlock.
Theory...

10
Build a Laboratory.
Once you have 6 or more scientists, the option to build a laboratory becomes available from the 'Construct Facility' menu. A laboratory will require 3 power, 6 scientists and 125 credits to build. Select an excavated section of your base and after the required number of construction days have passed, the achievement will unlock.

TIP: Having a base or full satellite coverage in Europe will reduce the required credits to 62.
...and Practice

10
Build a Workshop.
Once you have 6 or more engineers, the option to build a workshop becomes available from the 'Construct Facility' menu. A workshop will require 3 power, 6 engineers and 130 credits to build. Select an excavated section of your base and after the required number of construction days have passed, the achievement will unlock.

TIP: Having a base or full satellite coverage in Europe will reduce the required credits to 65.
Wet Work

10
Complete a Very Hard abduction mission in five turns or less on Classic or Impossible difficulty.
(6)
This can be a difficult achievement as finding a 'very hard' abduction mission can take time. To increase your chances, try and raise the panic level in one continent. The higher the panic level, the harder the mission will be.

As there is a limited number of maps and the rotation is random, it may also help if you wait until you receive a map you know well and are confident you can get through quickly. Just be sure to save your game at the base before launching the mission. Your soldier load out is entirely up to you but it is highly recommended you have a minimum of 5 soldiers and trying to clear a very hard mission with only 4 is near impossible.

The easiest way to beat the mission in five turns or less, is to start off by proceeding through the map learning what enemies are present and where they are located. Then reload the save you made at the start of the level and run through with that knowledge. Their positions and strategies may vary slightly but overall you should know what to expect.

TIP: Despite the option of Classic or Impossible, this will be much simpler on Classic
A Continental Fellow

50
Win the game from each of the 5 starting locations.
(14)
Each time you start the game you are given the option of what continent you wish to establish your base on. Each location has its own bonuses that can affect certain aspects of the game, but overall there is no great difference with each location.

This will take 5 playthroughs to unlock as long as you choose a different starting location with each new game. How you play and progress through the game is entirely up to you but be aware that you need to win the game. Having more than 8 countries pull out of the council will result in a loss and void that particular playthrough for this achievement.
What Wonders Await

5
Complete a Research Project.
This is story related and cannot be missed. After the 2nd mission you will be instructed to visit the lab where you will need to authorise a research project using alien materials. Either select the S.C.O.P.E or medkits. It will take several days to complete the project but you will receive a notification when it is ready and the achievement will unlock.
Up and Running

5
Build a base facility.
This is story related and cannot be missed. After the 3rd mission you will be instructed to build an alien containment facility. Once you give the go ahead and wait the required number of days, the achievement will unlock.
Combat Ready

5
Build an item.
This is story related and cannot be missed. Once you complete ‘What wonders Await’ you will be directed to the engineering department and instructed to build the item you just researched. Select the number of items you want made and the achievement will unlock.
Drums in the Deep

10
Gain access to the lowest level in your base.
(3)
To expand your base to the next level below, you need to build an access lift. Each access lift requires money (the cost increases with each additional lift) and will take several days to finish construction. There are only four levels, so once the fourth access lift has been constructed, the achievement will unlock. This will most likely come naturally as you progress through the game and expand your base.
Happy to Oblige

15
Fulfill a Council request.
Council requests will appear at random times via the situation room. These will involve a council nation requesting either alien technology/artifacts, items you can/have engineered, or satellites to be launched in exchange for rewards. Each request will carry a certain time limit allowing you to build/obtain the required items. Once you meet the requirements, the request will be completed and the achievement will unlock.

TIP: While most items will be fairly easy to build/obtain within the time limits, satellites will take longer to build then the allowed time, so it’s a good idea to always have a satellite in reserve so it can be launched quickly.

Also, the council requests are random, so if you receive a request that you don’t believe you can fulfill, don’t go out of your way, instead wait until an easier request comes along.
Tables Turned

10
Shoot down a UFO.
This is story related and cannot be missed. After the 3rd mission you will be called to mission command where you need to launch an interceptor to shoot down a UFO. Once you have confirmed the launch, it will engage the UFO and shoot it down, unlocking the achievement.
And So It Begins...

15
Complete the tutorial mission.
This requires you to complete the first mission. It is heavily scripted so as long as you follow the hints there shouldn’t be any problem. Once the mission is over the achievement will unlock.

NOTE: This cannot be done on Impossible, as selecting this difficulty skips the tutorial.

Meet New People. Then Kill Them.

25
Win a multiplayer match.
(66)
This requires you to win a multiplayer match and has to be done online. (no split screen/system link) The multiplayer consists of an allocated number of points which can be spent on creating a team of both human and aliens soldiers. The game will play out the same as the single player and will be over when one player eliminates all members of their opponent’s team.

This will require skill and strategy when going up against randoms but can be easily boosted by having one player skip their turn until all their soldiers have been killed.

To find players to boost this with click HERE
Xavier

10
Mind Control an Ethereal. Single player only.
(12)
Most important for this achievement is, that your Psi-Soldier has Psi-Inspiration as well as Mind Control and the Psi-Armor. You want your Psi-Soldier to have around 100 Will (more is better) with the Psi-Armor.

When you engage an Ethereal:
-Leave your Psi-Soldier out of sight of the Ethereal (even your Psi-Soldier can be mind-controlled and then you have to kill the Ethereal instead of mind controlling it yourself.)

-In the turn before you attempt the Mind Control, use your Psi-Inspiration so you get a +30 Will Buff.

-Then attempt the mind control.

TIP: You can also have a Support skill perk, "Combat Drugs". The smoke grenades of this Support add another 20 Will.
Angel of Death

10
Kill an alien while flying. Single player only.
(1)
This can only be achieved while wearing the Archangel armor, which is unlocked later in the game. The easiest class to use for this is the sniper with the headshot ability, as this will give you the greatest chance to kill an enemy without getting too close.

TIP: You may want to make a save at the start of the previous round before attempting this achievement in case the shot misses.
Beyond the Veil

10
Find a soldier with the Gift.
(7)
This is story related and cannot be missed. To do this you need to send one of your soldiers to the Psi-Labs. The soldier with the highest 'Will' is chosen to have the gift. This will mean that the soldier you choose will be out of action for 10 days, so be sure it isn't your main soldier if you are also attempting 'Ain't no Cavalry Comin.'
Prisoner of War

10
Capture a live alien.
(2)
This is story related and cannot be missed. Before attempting this you need to research the ‘Arc Thrower’ via the lab. (Researching the arc thrower is story related and will be available after researching Xeno-Biology) One the research is complete, construct it in engineering and outfit it on a soldier for the next mission.

Once you are in a mission you need to be close to an alien, (3 or 4 spaces from them and have a clear LOS.) Unless an alien approaches you, you will need to move close on your first turn, then use the arc thrower on your second turn. Press to select the arc thrower and fire. You only get one shot and there is still a chance you will miss so either reload a save, or have a second soldier standing by to try again if the shot misses. Otherwise the alien will go down and the achievement will unlock.
The Gatekeeper

10
Stun an Outsider.
This is a story related mission and cannot be missed. Outsiders are only found on crash-site missions and will reveal themselves when you move within range of one. Use the same method as ‘Prisoner of War’ but be sure to stun an outsider.
X Marks the Spot

10
Uncover the alien base's location.
This is story related and cannot be missed
See All, Know All

10
Build the Hyperwave Relay.
This is story related and cannot be missed
On the Shoulders of Giants

10
Build the Gollop Chamber.
This is story related and cannot be missed
Ride the Lightning

10
Build a Firestorm.
In order to build a Firestorm, you will first need a power core from a UFO or Alien Base. (It needs to be a working power core. A damaged one recovered from a downed UFO will not work.) This will allow you to research 'New Fighter Craft.' Once the research has been completed, construct a Firestorm from the Hanger menu. Once the required days have passed, the achievement will unlock.
Poison Control

10
Cure poison on five soldiers in a single mission. Single player only.
(19)
Before attempting this, you will need to research/build medikits and equip at least five when on the load out screen. It is highly recommended you use a Support soldier with the 'Field Medic' perk as this will alow a single medikit to be used three times instead of once

The easiest way a soldier can become poisoned is by a Thin Man so it is a good idea to attempt this in an early objective based mission. (The Thin Men seem to be the main enemy in these missions.) There are two ways to be poisoned, either have a Thin Man spit poison at you or after you have killed one, move your soldier into the poison cloud it leaves behind.

Once a soldier becomes poisoned it must be treated by a soldier carrying a medikit. Just be sure that the soldier running into the cloud can't be carrying a medikit as this will make them immune. When five soldiers have been cured of poison, the achievement will unlock.

TIP: An easier method to achieve this is to try and isolate a Thin Man and have at least five of your soldiers close by. Have your first soldier move in close and make the kill. Once the Thin Man is dead and has left behind a cloud of poison, move each member within the cloud. On your next turn, set about curing everyone. Be sure to make a save before attempting this as it may take several tries.

Note: This does not have to be 5 soldiers. It can be done with 1 soldier, 5 times. Just do a Bomb Disposal mission with all Thinmen. Had 1 soldier run in to the poison and out, cured then back in to get poisoned again. Done this way, each cloud is good for 2 poisonings.
And Hell's Coming With Me

10
Successfully assault an Overseer UFO.
(4)
This is story related and cannot be missed
Off My Planet

25
Recover the Hyperwave Beacon.
This is story related and cannot be missed
The Volunteer

10
Make contact with the Ethereal hive mind.
(2)
This is story related and cannot be missed
Flight of the Valkyries

10
Win a mission with an all-female squad. Single player only.
(22)
Before setting out on a mission, make sure all team members are female. If you lack enough female soldiers to fill a squad, hire more from the barracks. (You can’t actually select male or female when hiring.) As long as you have an all female squad and win the mission, the achievement will unlock.

TIP: The easiest way to get female recruits would be to hire a new soldier from the barracks, then save when you have 1 day left before they arrive. Fast forward time and see if you get a female soldier. If not, just reload and try again as you will eventually get a female to appear.

Alternate Method: (Thanks to Creech)

The Flight of the Valkyries can be obtained with just one squaddie. I used a female sniper to get the Lone Wolf achievement and unlocked Flight at the same time.

NOTE: All members don’t have to survive the mission, as long as you win, the achievement will still unlock.

There are 5 achievements with a total of 100 points

New Friend

10
Complete Friends in Low Places.
(5)
During the first or second month (it will depend on how many missions you are offered in the first month,) you will receive a council mission and be given the option of a normal mission or the DLC mission. Select the DLC mission and complete it.

The mission follows the standard ‘extract VIP’ formula. The new character Zhang, will take on the role of the civilian and will only have the hunker down ability. The map is very smaller and has only minimal enemies, mostly Sectoids and Thin Men. Just be careful towards the end of the mission as a Chryssalid will show up. Once Zhang reaches the Skyranger, the achievement will unlock.
Bait the Hook

10
Complete Confounding Light.
The next council mission you receive will be Confounding Light and will require you to activate 4 beacons and then proceed to activate the train’s main controls. The map is very similar to the other train station one encountered throughout the game. Again the enemies will be basic Sectoids and Thin Men, however this mission will have Mutons show up towards the end of the mission. Overall this is a relatively simple mission to anyone familiar with how the game is played.

NOTE: You aren’t required to bring Zhang along on this mission in order to unlock the achievement.
The Bigger They Are

20
Complete Gangplank.
After completing Confounding Light, the next council mission will be Gangplank. This mission takes place on a large Battleship, the layout of which is the same as the Battleship encountered in the late stages of the vanilla game. The mission requires you to deactivate 6 engine components, this is done by moving to an adjacent title and manually deactivating it or by using an explosive weapon.

This mission will have a range of enemies including Sectoids, Thin Men, Cyberdisks and Mutons but overall shouldn’t prove too difficult as there aren’t a large number of enemies and most of the time you will engage them one or two at a time. Once the 6th component has been deactivated, the achievement will unlock.

NOTE: You aren’t required to bring Zhang along on this mission in order to unlock the achievement.
Rising Dragon

30
Take your new ally into the final challenge.
(6)
All that is required for this achievement is to ensure you have Zhang in your squad when launching the final mission on the temple ship. Once the Skyranger lands and you have control of your squad, the achievement will unlock.

NOTE: This is missable because if you don’t have Zhang included in your squad, you will be forced to either load an earlier save or restart the entire game. Also be sure that Zhang doesn't die if you take him on missions prior to the final mission. If he does, you will be forced to reload a previous save or restart from the beginning.
All Aboard

30
Complete Confounding Light with more than 3 turns left on the timer.
(3)
The mission begins with 10 turns on the timer and the achievement requires you to finish with more than 3 turns left by the end. Unlike most other missions, this mission doesn’t require you to eliminate all enemies on the map in order to finish, instead, all that is required is the 4 beacons and the train controls be activated. I highly recommend you save your game at the start of the mission so that in the event you don’t meet the requirements, you can reload and try again, otherwise you will need to start a new playthrough.
The method to completing this will depend largely on the type of classes in your squad and your general play strategy but you will need to play offensively. A good strategy is to have 2 or 3 soldiers move up the interior of the train, 1 soldier move up the right hand side and 2 soldiers, preferably one of them a sniper, move up the left hand side or along the top of the train.

The main focus of 1 or 2 of the soldiers inside the train should be to dash to the beacons while only firing on enemies as a last resort or to help thin the herd and using the 3rd to protect the others. The occasional enemy will take up cover inside the train but most will take move to either side allowing you remaining soldiers to engage them. You should be able to activate the first 2 beacons with 7 or 8 turns left on the timer. Some time after activating the 2nd beacon, a muton will show up. (It’s position may vary slightly but will most likely show up on top of the train. If you have a soldier moving along the top of the train, this won’t be too much of an inconvenience. However, if you don’t, then at this stage i suggest moving all your units into the train as a muton with a height advantage can be deadly.

Keeping pushing through the train with at least 1 soldier dashing to the 4th beacon and another dashing for the very front of the train. Once all 4 beacons are activated, use your furthest soldier to reach and activate the main controls. Provided you have 4 or more turns left on the timer, the achievement will unlock.

Overall this is the hardest achievement as it requires you to take some degree of risk and is based on luck of shot outcomes.

TIP: You aren't required to clear all enemies in order to finish the mission, so if an enemy is out of range or doesn't pose too greater threat, leave them and concentrate on the beacons. Also having 6 squad members will make this achievement significantly easier than attempting it with only 4 or 5 soldiers.