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