Here is the full list of all 19 Demonologist achievements.
Buy the Pub.
Play on the Hospital map
Play on the Cyclone Street map.
Purchase Two Crucifix
Exorcise the ghost once.
Take Two Photos Of The Ghost.
Correctly identify the ghost 3 times.
Correctly identify the ghost once.
Read EMF Level 5.
Die once.
Play on the Abandoned House map.
Exorcise the ghost 5 times.
Buy the Lighthouse.
Revive your friend with a Tarot Card.
Successfully joined the "family."
Play on the Bedlam map
Exorcise the ghost in the Bedlam
Play on the Kurosawa House map