So if you could have a mythical or movie monster taking on a pony form, what would it be?

Bonus Question: If you could take any character from the show and have it be the monster pony you mentioned previously, what would that pony be (Background ponies, Side ponies and Mane 6 are allowed)?

Some vicious werewolf chick turning into a vicious marewolf and killing ponies.

6259184 Werewolf/Marewolf is always a good option. If you had to pick a character from the show to be turned into such a beast, who would it be?

Someone willing to rip ponies throats out, of course. No idea who specifically; a hit man or something similar.