Here is the full list of all 38 Happy Lab achievements.
Destroy Body Part
Deal Damage with a Mine
Use the Crossbow
Use the Minigun
Use the Grinder
Deal Damage with a Spikes
Deal Damage with a Pusher
Deal Damage with a Spring
Use the Plasma
Teleport Dummy
Use the Magnet
Make Damage
Deal Damage with the Creepergun
Destroy all Body Parts
Deal 5k Damage with Flamethrowers and 2k with Flamer
Deal 5k Damage with Iciclethrower
Earn 1k $
Earn 10k $
Earn 100k $
10 seconds don't Touch the Floor
The Dummy is Affected by a Flamethrower and an Iciclethrower at once
Roast a dummy with a Flamethrower
Build a Cube
Deal Damage with a SMG
Unlock all Traps, Skins and Armors
Deal 10k Damage
Take Damage from 3 Springs in a row
Take Damage from 3 Pushers in a row
Deal 2.5k Damage with Flamethrowers
Deal 2.5k Damage with Spikes
Deal 2.5k Damage with Pushers
FatalityMinehint
Finish the game #1
Finish the game #2
Finish the game #3
Perform 10 Fatalities
Finish First Chapter
Finish First Level