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