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