Here is the full list of all 23 Iron Brigade (GFWL) achievements worth 250 gamerscore.
Completed Mobile Trench training.
Defeat the Northern Pylon.
Defeat the Guardian of the Southern Terminal.
Defeat Vlad.
Earn $20,000 from mission completion rewards.
Collect 10,000 Scrap.
Complete a mission with 4 players.
Complete 10 Missions with 2 or more players.
Defeat the Northern Pylon with 2 or more players.
Defeat the Guardian of the Southern Terminal with 2 or more players.
Defeat Vlad with 2 or more players.
Defeat 3500 Monovisions.
Kill an enemy with a ricochet sniper shot after 4 bounces.
Destroy 5 Enemies with a single explosion.
Earn a Bronze Medal on every mission.
Earn a Silver Medal on every mission.
Earn a Gold Medal on every mission.
Purchase an item in the store.
Complete a mission while wearing the uniform of an elite PSI agent.
Complete a solo mission without firing a shot.
Defeat the Martian Bear.
Complete wave 20 on Survival: Swamp.
Complete wave 30 on Survival: Settlement.