Onomatopoeia

Well, Ben Affleck and Matt Damon are good pals. And Kevin Smith is friend to them both. So what if Damon played a character created by Smith, a character who can match Batman in a fistfight and who also makes the best of any gun available?

This character is Onomatopoeia and he is, basically, a killer of non-superpowered superheroes. And that is why he would be a perfect villain for Batman. Given the origin of his name (origin that is pretty literal for that matter), it would be very interesting. Furthermore, Onomatopoeia would also pose a different kind of threat to Batman, besides the physical one.

Thus, in order to find out the secret identity of Batman, he creates a second one for himself. In this way, as a new vigilante, he actually finds out that the Dark Knight is Bruce Wayne.

Kevin Smith already said that this character does not translate too well to the TV screen. However, we are talking about the silver screen now. And if anyone can do it, Ben Affleck can. With Matt Damon playing the role.