Here is the full list of all 9 The Haunting of Billy achievements.
Look at that lil' devil!
Have on you 250 candy at one time.
Find your way off the level.
Blow an enemy clean off the level.
Find and equip Bucky's pan.
Wear a full costume set.
Don't take Bucky with you.
Wear a full costume where every piece is unique.
Meet your loving and caring guardian demon.