Here is the full list of all 38 Halloween Forever achievements.
Find all six hidden runes for a secret ending!
You won as A Skeleton! I knew you had it in you (I can see through your ribgaps).
Beat a world without taking a hit.
You won as Ms. Witch! Hope you had a feline time.
You bested Necroking! The return of Necromancer! How the mighty have fallen.
You bested Blue Devil! Necessity is the moth of invention.
You bested Frog King! I toad you so!
Set loose 666 cats as Ms. Witch.
You rescued A Skeleton! A bony vertebra buddy.
Run away from a crow for a very long time.
You bested Manleech! Say your lamprey-ers!
You rescued Ms. Witch! She has endless cats!
Trigger spike traps 101 times.
You rescued Butternut Bro! Your gourd from another lord.
Knock five spiders off the wall.
Wake up 6 sleepy frogs.
You bested Necromancer! Back to ghoul school with you, fool!
You bested Eyeskuller! Eye spy with my little eye something that's about to explode!
You bested Red Devil! Yow, it's hot in here!
You bested Green Hydra! Two heads are better than none, but that won't slow us down.
Destroy a breakable wall.
You bested Big Bat! Have you ever seen a bat so big?
Destroy five hanging skeletons before they hit the ground.
You bested Chainsaw Megamaniac! There's no chainsaw maniac tougher than this one.
Make Chainsaw Megamaniac leave his chainsaw behind when he dies.
You won as Butternut Bro! Way to squash the opposition.
Never harm little bats! Ever!
Beat the game with 1 HP Mode enabled! HARDCORE!!!
Get grabbed by Blue Devil three times.
Watch Manleech vomit 10 times. Yucky!
You won as Pumpkin Man! Get pumped!