Here is the full list of all 28 The Boogie Man achievements.
Speak to all the characters before the event in the study
After the phone call, go back to the dining hall and speak to the characters
Witness Brendon's murder in the great hall
Take care of Stevie
Inspect all of the servants' corpses
Get Game Over while using Keith
Get Game Over while saving Lance
Save Lance
Try to enter the room with the bodies while together with Lance
Save Sophie and Richard
Save David
Kick and break the boards in the room with the water pressure control panel
Save Shirley
Go back to the room to speak with Lance after Shirley wakes up
Try to go back while moving through the pipes with David
Use the music box key on the clown
Inspect the toilet in the bathroom before starting the search for Sophie
Speak to Sophie in the room one more time after saving her
Try to enter the room where Sophie is locked in with the dog while together with David
Read all of the red messages
Return to the room where everyone is to speak after David dies
Lose a battle with the Boogie Man
Get Bad Ending 1
Get Bad Ending 2
Get Bad Ending 3
Get Bad Ending 4
Clear all conditions for the Good Ending
Get the Good Ending