Here is the full list of all 16 Boodunnit achievements.
Complete the tutorial
As a rat, Climb on Mr. Boonkle’s statue
Complete the Cemetery Level
At the cemetery, scare a human until they pass out
Collect a clue
Collect all clues in the game
NEW_ACHIEVComplete the Crime Scene LevelEMENT_DESC_1_6
As a bird, use the air vent to reach the top of a building
Scare a police officer
When possessing a cop, try to talk to vincent
Complete Boodunnit?!
Collect the Cake clue
Collect the Knife clue
Collect the Hard hat clue
Collect the Scrap of Coat
Collect the Broken Flower Pot