Here is the full list of all 23 Foreign Legion: Buckets of Blood achievements.
Kill 25 chickens
Finish the campaign on any difficulty
Purchase an outfit, helmet and accessory
Kill all chickens in one round
Make 15 headshots in one round
Kill all enemy waves in 7 minutes
Kill 5 enemies with an air raid
Beat the Village in the extreme difficulty
Find the minigun
Win the game with all civilians alive
Make a kill chain of 10 kills
Kill 4 enemies with one rocket
Repair the town hall 5 times in one round
Escort the bus safely without it taking damage
Reach level 20
Purchase the Foreign Legion FAMAS
Destroy the supreme chicken overlord
Kill 1337 enemies in total
Survive 30 minutes in endless mode
Kill 2500 chickens
Play a game with only the Smiley Badge equipped
Play a game with only the Night Vision Goggles equipped
Play a game with only the Peace Badge and Bullets equipped