Complete each achievement to get the allotted gamerscore.

Unlockables

Assault Flags (10) Single Player: Collect all of the Flags scattered throughout the game.
Escapist (25) Zone Battle: Defeat all spaceships in Areas 29 & 30: Medium or Hard difficulty in one session.
Fearless (20) Single Player: Complete 3 sequential areas on foot: Medium or Hard difficulty in one session.
Heroes Campaign (30) Co-Op Campaign: Complete all areas on Hard difficulty with the help of a friend.
Hot-wired (5) Single Player: Capture all 3 hijackable vehicles at least once.
Ice Cold (10) Single Player: Freeze 50% of infantry in any Zone: Medium or Hard difficulty in one session.
Moby Dick (5) Single Player: Destroy the Mecha Orca.
Pyromaniac (10) Single Player: Burn 50% of infantry in any Zone: Medium or Hard difficulty in one session.
Smoothie Heroes (20) Co-op Campaign: Kill 100 infantry, one player freezes & the other shatters, on Hard in one session.
Underground Hunters (20) Co-Op Campaign: Finish all underground areas with the help of a friend: Medium or Hard difficulty.
Wonder twins (20) Zone Battle: Use all 4 Co-Op attacks, kill 10 units with each: Medium or Hard in one session.
Zoned Out (25) Zone Battle: Complete 6 Zones, each with the help of a different LIVE enabled friend.