Wolverine

Being a mutant, Wolverine is, of course, classically associated with the X-Men. However, in more recent times, he has also been a member of the Avengers and did, in fact, fight on the side of Earth’s mightiest heroes against the X-Men in the Avengers Vs X-Men arc.

The character, also known as James “Logan” Howlett, joined in New Avengers #6 in June of 2005 and has mostly maintained simultaneous membership of various Avengers teams and the X-Men ever since.

Of course, in terms of movies, the character has only ever appeared in Fox’s X-Men franchise – with Hugh Jackman’s version of Wolverine representing the franchise’s flagship component. There is a possibility, however, that a new actor might portray him in the Marvel Cinematic Universe in the future, which would mean joining the Avengers on screen – and that would be amazing to see.