Single Player and Co-Op Achievements
A Monument To All Your Sins (150G): Complete every mission in Halo Reach alone on Legendary difficulty. Very self-explanatory. And difficult.
Banshees, Fast and Low (25G): Hijack a Banshee in campaign. There are a few places to do this. The easiest is probably the Tip of the Spear mission once you enter the Spire’s shields. There are a couple Banshees here that will dive at you if you stand on the highground.
Blaze of Glory (25G): Achieve 200,000 points in a Firefight game. Can be cheesed by choosing options that make Firefight easier.
Crowd Control (10G): Earn a Killionaire medal in Firefight. This means you have to kill 10 enemies within four seconds of each other. Not too hard to manage against Grunts.
Doctor, Doctor (5G): Replinsh health using a Health Pack. Easily done at numerous points in both campaign and multiplayer.
Dust and Echos (10G): Complete the 8th mission on Normal or harder.
Firestarter (10G): Score 50,000 points or more in Firefight.
Folks Need Heroes (50G): Complete the Campaign on Heroic difficulty.
Game, Set, Match (25G): Complete a Firefight mission on Legendary without dying.
Gods Must Be Strong (125G): Complete the campaign on Legendary.
Heat The Pipe (75G): Score 1,000,000 points in a Firefight game. You may need to turn on options like unlimited ammo in order to manage this one.
I Didn’t Train to Be a Pilot (10G): Take out 3 anti-aircraft guns during the 8th mission. This is the one in which you pilot a Falcon around New Alexandria.
If They Came to Hear Me Beg (25G): Perform an Assassination against an Elite to survive a fall that would have been fatal. No, seriously. You can earn this achievement at the beginning of the last mission. There is a cliff overlooking some Grunts and one Elite. Sprint off the cliff, aim for the Elite, and hit your Melee attack button just as you land behind him. Needless to say, you may need to try this one a few times to get it right.
I Need a Weapon (10G): Complete the 4th mission on Normal or harder.
Into The Howling Dark (10G): Complete the 7th mission on Normal or harder.
Keep It Clean (5G): Kill 7 Moa during the 2nd mission. The Moa are the Ostrich-like birds. You’ll have to mow down just about everyone Moa you see to earn this achievement.
Lucky Me (25G): Earn a Triple Kill while Jetpacking. Also can be earned in some multiplayer matches.
Protocol Dictates Action (10G): Complete the 3rd mission on Normal or harder.
Score Attack (10G): Earn 15,000 points in Score Attack Firefight Matchmaking. You’ll probably have to co-op with other players to manage this achievement.
Send me Out…With a Bang (10G): Complete the 10th mission on Normal or harder.
Swap Meet (10G): Trade weapons with an AI ally in Campaign.
Tanks Beat Everything (25G): Finish the 9th mission on Legendary with the Scorpion intact. You don’t need to actually use the tank all the way through, however. The easiest way to earn this achievement is to park the tank if it is becoming heavily damaged and then clear out the level using other methods. Then go back and pick up the tank afterwards. You’ll earn the achievement once the tank arrives the Sword Base gate.
The Soldier We Need You To be (25G): Complete the campaign on normal difficulty.
You Flew Pretty Good (10G): Complete the 6th mission on Normal or harder.
Your Heresy Will Stay Your Feet (25G): Kill the Elite Zealot before he escapes during the 5th mission.