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