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