Here is the full list of all 12 Alien Breed Episode 3: Descent achievements worth 200 gamerscore.
Took 500 damage without dying
'Vengeance' completed in 17 minutes or less
Single player completed on Elite difficulty
Single player completed
Found all secret collectibles
Picked up all the logs
Killed 1000 aliens
Completed a level in multiplayer
Killed 5 aliens with one Frag Grenade
Killed 250 aliens during multiplayer Survivor mode
Stayed alive for 8 minutes in Survivor mode
Stunned 5 aliens with one Stun Grenade