Here is the full list of all 21 GARAGE: Bad Trip achievements.
Dispose of the old boss
Beat the game
Kill Demikhovsky
Find all the parts of Demikhovsky's diary
Pick up soap in the shower room
Kill Dreadnought
Ride the train
Unlock a combination lock
Find a condom
Smash 15 vending machines
Kill the centipede
Open the shelf in the desk
Find a secret passage
Take "heavenly" pills
Kill your first cadaver
Watch a TV show
Score a goal with your head
Complete the Labyrinth Challenge
Complete the Axe-man Challenge
Complete the Skirmish Challenge
Complete the Arena Challenge