Here is the full list of all 38 Possessed achievements.
Humble Man
Meet And Greet
Blow Some Shit Up
Custodian Dan
Evil Presence
Stairwell Of Death
Not The Best Half
Blow Holes
The Ol' Courtyard
Surprise
Didn't See That coming
Crazy Lady
Healing Power
The Shitter
Nurse To The Rescue
Join Us
Hanging From A Thread
Now It's A Party
More Ammo Needed
The Basement
Not You Again
Taken
Nest Of The Netherworld
Katie I'm Coming
Stone Crusher
Nothing Can Stop Me
6 Down
Time To Die
Welcome To Hell
Birds With Rockets
Fat Motherfucker
Hot In Here
Eternal Torture
Don't Fall
Don't Look Down
Hell's Design
The Chain Walk
Get Fucked