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