No One Left Behind Achievement in Halo: The Master Chief Collection

This achievement is best done cooperatively with 2-3 other players since the extra firepower will prove to be beneficial when eliminating the Covenant enemies in the area. In total, there are about 6-8 Marines that you will need to protect throughout the duration of the mission. They will generally follow you around and provide support, but take note that they aren’t necessarily strong enough to kill Elites, Hunters, and Jackals on their own. Despite this, with a 2-3 other players, protecting at least one Marine should be pretty easy.

As soon as the mission beings, you will notice that the area is actually a recycled environment from the Campaign’s “Forerunner” mission. Walk around to each of the small bases in the corners of the area to locate the Marines. Help them take out the immediate Covenant threat and once the Elites, Grunts, and Jackals are killed, the Marines will begin following you. At this point, two players should lead the Marines to the top of the central structure in order to hold the upper ground advantage over the Covenant. The third player (or other two players if you’re playing with a full lobby) should remain stationed on the ground in order to flush out the Covenant head-on.

From here on out, a few Covenant Phantoms will begin to drop off waves of enemies, some of which even drop of a Wraith. At the top of the central structure, there are a few Spartan Lasers and Rocket Launchers, both of which will be beneficial in eliminating the ground troops from afar. The players on the ground should arm themselves with a Plasma Pistol and Battle Rifle/DMR in order to pull off quick Noob-Combos on the Covenant Elites. With the group of players split between the top level of the structure and the ground level, you should have no problem killing the Covenant quickly while ensuring the Marines are kept alive. If at any point you think it’s necessary, go ahead and give one or two of the Marines a Rocket Launcher for safety. Also, the player(s) on the ground should eliminate the Elite Zealots (wielding Energy Swords) as quickly as possibly before the Elites storm the top of the structure and kill the Elites.

Towards the end of this mission, two Covenant Phantoms will linger overhead and you will be required to destroy them via Spartan Laser/Rocket Launcher before evac can arrive. Once these ships are destroyed, the achievement will unlock as you approach the Pelican so long as at least one Marine is still alive.