Here is the full list of all 18 OTXO achievements.
Clear a run on Impossible Mode
Clear a full run without taking any drinks
Unlock all drinks
Play fetch
Destroy the Heart
Collect all guns
Collect everything from the gachapon machines
Kill 50 enemies with kunai
Kill an enemy with a thrown magazine
Kill 15 enemies with doors without dying
Kill 50 enemies with grenades
Go fishing
Vault over 50 times
Order the ANIMAL drink at the bar
Clear a room without using Focus
Clear a room by only kicking
Roll over 100 times
Die for the first time