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