Here is the full list of all 21 The Expendables 2 Videogame achievements.
Upgrade all characters and signature weapons
Kill 2000 enemies using melee attack or grabs
Complete the Campaign on Casual difficulty
Complete the Campaign on Hardcore difficulty
Complete chapter 4
Complete all Challenges
Complete chapter 3
Complete chapter 2
Perform all 4 fully upgraded grab moves
Perform all grab moves, melee attacks and signature kills
Use each weapon in the game to kill an enemy
Kill 50 enemies in a single combo
Heal 50 times
Complete a mission on Hardcore without getting healed
Complete chapter 1
Play through an entire chapter with 4 player co-op
Take out the weapons train
Interrogate the sniper
Blow the factory gates!
Complete a challenge
Upgrade 1 character completely