Ash from Evil Dead is my number one, no question.

Other than that...Pinhead could be awesome.

Michael Myers would fit the "silent slasher" quota.

An oddball choice would be a tag team character of Sam and Dean Winchester of Supernatural fame. Produced by Warner Bros....just sayin.

I really dont know. MKX kinda had them all.

Alien, Predator and Jason were pretty high on the list and they are all in. We even got Leatherface. I dont know why.

So looking at who is left in horror/sci fi you have
Terminator - Would be a bit awkward because I doubt they'd pay for Arnie's likeness so it would be an endoskeleton, but then xrays would be screwed because you are fighting the skeleton already.

Robocop - somewhat easier to fit in then Terminator but would they be able to get 3 fight styles out of him? Plus it wouldnt be the real Robocop it would be modern one.

Chucky - Yoda.

Pinhead - maybe. Never really watched Hellraiser but he seems to be a bit Quan Chi anyway.

Scream guy - nope.

Thats all I can think of from movies that would kinda work in MK.

Comics
Deadpool - marvel guy so nope

Joker - maybe. if his ending implies he is like Emperor Joker or something.

Spawn - I dont like him but edgelords do.

Dont know who else really. Dont really want a load of guest characters.

No guest characters!

but obviously at this point that's not an option, so if i absolutely had to pick guest characters..

Spawn
Marv from Sin City ?

The Gorilla leader from Planet of the Apes.

Sure they do guest characters again. If they do, i hope they are from other games. Like Killer instinct for example. But sofar WB wants the movie hype as that makes more $. I just hope they are characters that fit the game.

Maybe Godzilla and/or Spawn.

Bruce Lee

Watch for Pennywise to be a guest in MK11 lol.

Nightking from Game of Thrones, too good to pass up.

Gazelle (from Kingsman: The Secret Service). Loved the blade style prosthetic lower legs.

This is a weird choice, but Trevor Phillips from Grand Theft Auto 5.

I always envision his X-Ray would be how he killed Johnny Klebitz, he chokes them, throws them on the ground and chucks a beer bottle at them. His stomps would be shown X-Ray style with the last hit on the opponent's head.

One of his variations would be Rampage where a move increases the power of his hits. Most of his special moves would include a shotgun and grenades, similiar to Stryker and Erron Black.

A fatality would have him jamming a flare into the opponent's throat and calling on Ron, his friend. Ron would fly a plane and fire a machine gun shredding the opponent to pieces.

His second fatality would include shooting a submachine gun shooting off their parts and ending with a headshot that makes the head explode.

Even though Mileena is dead, I thought of an intro dialogue if he was in MKX

Mileena (takes off her veil): Repulsive human!

Trevor (cocks a shotgun): Says the one with the butterface

Mileena: I'll eat you alive for that!

An intro with Leatherface

Leatherface revs up his chainsaw and dances

Trevor: And I thought the Altrusits were nuts!

Just a really weird idea I had.