Here is the full list of all 32 Hell Pie achievements.
Get all outfits
Defeat the Hell Pie
Collect everything
Collect all Candymeat
Collect all Unilambs
Collect all Lucky Cats
Destroy the crosses in Heaven
Complete the Wing Horns Challenge Level
Witness a dark ritual
Use private insurance
Unlock Nugget Fart
Bring all sexy plants together
Complete the Arm Horns challenge level
Plug in all Wi-Fi sticks
Defeat Gluttony
Complete the Light Horns challenge level
Monty Python did it with style, don't know how it's done here
Collect 10000 crystals
Complete dining room side quest
Hit 10 humans in the factory
Buy your first outfit
Trigger whale explosion
Collect 5000 crystals
Complete the Ram Horns challenge level
All Munchers freed
Defeat the boss of the Sewers
Collect 1000 crystals
Complete the Sprint Horns challenge level
Collect your first ingredient
Smash Nugget against the wall
Meet Cupid
Meet Chef