5) Killgrave
One recurring criticism of Marvel’s movies is the lack of great villains (apart from Loki, of course). By contrast, the TV shows – particularly the Netflix ones – keep dishing out well-characterized antagonists. David Tennant’s Kilgrave, as seen in Jessica Jones, is one of the best of the lot… which is why it would be great to see him in the films.
In the comics, the mind-controlling Zebediah Killgrave AKA The Purple Man is a frequent foe of The Avengers. As such, it would make sense for him to face up against the big guns, as well as Jessica Jones.
Seeing as Jessica’s personal story with him wrapped up in JJ season one, a new take on the character could see him being reborn in all his purple-skinned glory. If his main goal was world domination rather than a mere infatuation with Jessica, he could be one of the team’s most unstoppable foes.