Finished the Fight Achievement in Halo: The Master Chief Collection

This achievement will unlock once all nine missions of the Halo 3 Campaign have been successfully completed on either a Solo Legendary playthrough or Cooperative Legendary playthrough. There are multiple methods in tackling the missions of the Campaign, but keep these general tips in mind when playing:

• Utilize the Noob-Combo (Plasma Pistol/Battle Rifle) at all times when facing Brutes; an overcharged Plasma Pistol shot will drain their Power Armor, and a quick three-burst shot headshot will down the enemies easily
• Utilize ground vehicles – Warthogs, Scorpions, and Ghosts – as frequently as possible; their firepower in missions such as Tsavo Highway, The Covenent, and The Ark will help clear out areas quickly and you can even drive past enemy encounters if the mission allows for it
• When facing Hunters, get close enough so that they charge at you, allowing time to side step their attack; when the orange flesh on their back is exposed, shoot it, as this is their only weak spot
• When squaring off against the Flood, keep a Shotgun on hand; it’s the best weapon to use against the parasite
• Don’t neglect the basics of using cover; when your shields drop down, hide behind a wall or crouch behind an object before charging back out into battle
• Try exploring the levels and finding alternate routes behind or around the enemies; this can help save time by skipping major firefights on levels such as Sierra 117, The Storm, The Covenant, and The Ark

Overall, because seasoned Halo players will be familiar with both level design and enemy behavior, completing the entire Campaign on Legendary will be quite easy. If a text-based walkthrough is necessary, be sure to visit THIS GUIDE for further assistance with this achievement. Once all the missions in Halo 3 have been completed on the Legendary difficulty setting, this achievement will be yours.