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