Here is the full list of all 15 Hell Loop achievements.
Finish first three levels
Kill 50 humans
Kill 500 Humans
Kill 5000 Humans
Catch all humans
Unlock second spawn gate
Do not kill anyone
Upgrade one trap at least to level 5
Finish all levels
Remove armor on everyone in one level
Pause the game at least 20x during one level
Finish the game with no restart difficulty
Finish the game with no escape difficulty
Finish the game with no escape and restart difficulty
Kill 50000 Humans