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