Complete one of the following achievements to collect their Xbox Live Gamerscore points:
Unlockable: --- How to Unlock:
117 (40 GP) --- Earn all Gold stars in all operation missions.
Archeology (20 GP) --- Complete Operation F.
Brute Force (20 GP) --- Finish the objectives using only the Brute Shot, melee and grenades in Operation D, Mission 1.
Distinguished Service (30 GP) --- Earn all medals in the game at least once.
Dynamic Duo (60 GP) --- Earn all Gold stars in all co-op missions.
Escort Service (20 GP) --- Keep all Wolverines intact in Operation A,
Evacuated (20 GP) --- Complete Operation D.
Extermination (60 GP) --- Kill 10,000 enemies in co-op.
Extra Credit (20 GP) --- Complete 75 challenges.
Flooded (60 GP) --- Complete all co-op missions.
Foot Soldier (20 GP) --- Finish the objective without using any vehicles/turrets in Operation E, Mission 4.
Immune (100 GP) --- Finish a co-op mission without becoming infected.
Never Knew What Hit Them (20 GP) --- Kill a convoy target with every stationary gun in Operation C, Mission 3.
Nowhere to Hide (20 GP) --- Prevent all Jackals from regenerating their shield in Operation B, Mission 3.
Overachiever (100 GP) --- Earn all co-op medals at least once.
Overrun (20 GP) --- Complete Operation A.
Pension Plan (20 GP) --- Earn 25000 Spartan Points throughout your career.
Powered by MJOLNIR (20 GP) --- Use every ability at least once (excluding Overshield and Seeker Drone).
Prodigy (20 GP) --- Earn your first Gold star in an operation mission.
Recruit (20 GP) --- Earn a star of any type in an operation mission.
Silvertip (20 GP) --- Destroy all Mega Turrets with the Grizzly tank in Operation F, Mission 2.
Skull Combo (20 GP) --- Complete any mission with the maximum number of Skulls active.
Switched Off (20 GP) --- Complete Operation C.
Switched On (20 GP) --- Complete Operation B.
Terminated (20 GP) --- Complete Operation E.
The Company of Strangers (20 GP) --- Complete a co-op mission with at least 5 different players.
The Enemy of my Friend (100 GP) --- Get a higher individual score than your partner on all co-op missions.
Vidmaster Challenge (30 GP) --- Complete Operation 5,
with the Hollow and Black Eye Skulls active. Mission
Vidmaster Challenge 2.0 (30 GP) --- Complete Operation F, Mission 4 with the Blind and Thunderstorm Skulls active.Weapon of Choice (10 GP) --- Score a kill with every handheld weapon (excluding Rocket Launcher and Spartan Laser).