Source: comicbook.com
6. Mephisto
Man, I wish the Marvel Cinematic Universe would go whole hog and introduce the for real devil. Can you imagine what a power move that would be? "Ah, yes, in the next Avengers film, Captain America is going to punch the Devil right in the face."
Anyway, Mephisto isn't technically the Devil but he's about as close as you can get. He's also already been in two movies, it's just that those were the Ghost Rider movies and no one cares or remembers. Mephisto first appeared to menace the Silver Surfer in his more philosophical title, but he soon locked down his role as the go-to devil for all Marvel comics.
Well, except X-Men but that's because they got their own s**t going on.
An MCU Mephisto would fit in well as a Doctor Strange villain, but could also be an Avengers level threat.
