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