Here is the full list of all 43 Foreign Legion: Multi Massacre achievements.
Kill 1000 zombies
Snipe 250 prairydogs
Snipe 100 prairydogs
Start the Generator 100 times
Snipe 25 prairydogs
Start the Generator 50 times
Make 250 fueltanks explode
Make 100 fueltanks explode
Break 250 wooden boards
Make 1000 enemy headshots
Host a 3 player game
Host a 4 player game
Start the Generator 25 times
Kill 250 zombies
Shoot off 250 zombie limbs
Wear the BunnyEars and jump 500 times.
Honk your clowns nose 500 times.
Make 250 enemy headshots
Make 25 fueltanks explode
Break 250 tombstones
Pop 250 pumpkins
Break 100 wooden boards
Break 100 tombstones
Shoot off 100 zombie limbs
Kill 25 zombies
Break 25 tombstones
Shoot off 25 zombie limbs
Break 25 wooden boards
Kill the ghost on time
Shoot 69 peacedoves
Pop 100 pumpkins
Make 50 enemy headshots
Shoot 30 peacedoves
Blow up 250 dolphins
Blow up 100
Pop 25 pumpkins
Finish a game in EXTREME
Blow up 25 dolphins
Shoot 7 peacedoves
Kill 250 players
Kill 100 players
Kill 25 players
Win a domination game.