Here is the full list of all 70 Happy Room achievements.
Kill dummy with a stake
Kill dummy with a mine
Kill dummy with a crossbow
Kill dumy with an acid gun
Kill dummy with a laser
Kill dummy with a shotgun
Kill dummy with a piranha
Kill dummy with a shuriken
Kill dummy with a mace
Kill dummy with a gravity gun
Kill dummy with a big rocket
Kill dummy with an axe
Kill dummy with a firegun
Kill dummy with a lightning
Kill dummy with a plasma gun
Kill dummy with a black hole
Deal 30000 damage in sandbox
Deal 20000 damage in sandbox
Kill dummy with a spikes
Kill dummy with a rocket launcher
Kill dummy with a grenade launcher
Kill dummy with a jumper
Kill dummy with a wall
Kill dumym with a ice gun
Kill dummy with a deathray 3000
Kill dummy with a monster
Kill dummy with a saw
Kill dummy with a minigun
Kill dummy
Complete tutorial
Explode a mine
Complete the first achievement
Get 60 achievements
Get all 120 achievements
Kill dummy with a disco ray
Get all fatalities
Throw dummy for 50 meters to the left
Throw dummy for 50 meters to the right
Throw dummy for 50 in the air
Hit a bird
Kill dummy with a guillotine
Reach the Moon
Kill dummy with a wheel
Kill dummy with a pitchfork
Kill dummy with a spider
Kill dummy with a fish
Kill dummy with a hay
Kill dummy with a goblin
Kill dummy with a magic wand
Kill dummy with a dragon
Kill dummy with a sheep
Kill dummy with a tesla
Kill dummy with a bomb
Complete 48 dungeon achievements
Complete all 97 dungeon achievements
Kill dummy with a spring
Kill dummy with a static mace
Complete 38 armory achievements
Complete all 76 armory achievements
Master of miscellaneous weapons
Master of elemental weapons
Master of explosion weapons
Master of fire guns
Master of cold weapons
Master of all weapons