Here is the full list of all 20 Infested Nation achievements.
You executed the prisoner.
Complete a level using only a knife.
Complete a level using guns only.
You found an egg!
Complete the game.
Complete the first mission.
Complete the second mission.
Complete the third mission.
Complete the fourth mission.
Complete the fifth mission.
Complete the sixth mission.
Complete the seventh mission.
Complete the eighth mission.
Complete the ninth mission.
Complete the tenth mission.
Complete the eleventh mission.
Complete the twelfth mission.
Complete the thirteenth mission.
Complete the fourteenth mission.
Complete the fifteenth mission.