Here is the full list of all 16 Gunpowder Punk achievements.
Kill 1000 enemies
Get 100 fast enemy kills
Clear 100 game levels
Unlock 10 cybernetic upgrades
Unlock all available cybernetic upgrades
Collect total 50000 score
Collect total 500000 score
Defeat Bloody John
Defeat Ike the Ripper
Defeat Fire Crasher
Defeat Tormentor
Defeat Boneripper
Defeat the game
Survive 2 minutes in the arena
Survive 5 minutes in the arena
Survive 10 minutes in the arena