Here is the full list of all 26 Paper Cut Mansion achievements.
Reach Floor6
Reach Floor5
Reach Floor4
Solve A Riddle
Unlock Vending Machine
Die for the very first time
Reach Floor3
Unlock An Evidence Piece
Reach Floor2
Solve A Musical Lock
Gain A Medal
Unlock An Equipment Card
Unlock Father Papotto
Defeat 10 enemies
Defeat the Hat Man
Die 10 times
Complete Normal mode
Complete Hard mode
Complete Very Hard mode
Unlock All 27 Endings
Defeat 100 enemies
Defeat 500 enemies
Unlock All Equipment Cards
Unlock All Evidence
Gain 1000 coins
Solve 50 locks