There is way too many characters and I'm pretty sure all of my sanity is gone IDK this is pre MQSG writing this.

XGaster

XChara

XAlphys

XUndyne

XMettaton

XMuffet

XToriel

XAsgore

XAsriel

Xfrisk

XPapyrus

Cross Sans.

Nightmare Sans

Horror Sans

Killer Sans

Dust Sans

Z!Insanity Sans

Error Sans

Classic Sans

Fell Sans

Outer Sans

Underswap Sans

Ink Sans

Fresh Sans

Storyshift Chara.

Dream Sans and if you bring a black apple to Dream and force him to eat it then we will get Shattered Dream Sans.

Epic Sans

Core Frisk

Fatal_Error Sans

Geo Sans

Tear in the Rain Sans

Gaster.

Dustswap papyrus

Outerdust Sans

Dustfell Sans

Color Sans

Seraphim Sans

Alphatale cast

Error404 Sans

Omnipotent Sans

Alpha Sans/ Judge alpha Sans.

King multiverse sans/King Chaos

Infected Sans

Faker 404

Ten no Kami

Godverse cast

Sans the skeleton or Godverse Sans

Virus 404

King Godverse

Queen Godverse

Everything Sans