MCU: 10 Best New Villains Who Could Join Phase 4

10. Mr. Sinister

Strictly speaking, we should have probably seen Mr Sinister by now in Fox's X-Men movies, as his presence was teased at the end of X-Men: Apocalypse, which most assumed was going to lead to his appearance in Logan's dystopian future. But he was conspicuously left out and now the mainline X-Men movies are moving on to the Dark Phoenix saga, so his time may have passed.

He's still a big enough villain to come to the MCU though, and he's almost big enough to warrant a cross-over event with the Avengers if that's how Marvel choose to introduce the mutants.

He's immortal, all-powerful and a genius capable of besting the X-Men fairly easily, and his penchant for cloning could be used as a means to introduce him to the existing universe. After all, the idea of someone trying to harvest superhero genes to breed his own army is a pretty damn compelling one.