Ant man/Giant man is actually pretty ****ing awesome. Can be small or large or in between, depending on which fight he's doing. That makes for some pretty cool ways for him to fight (can shrink out of someone's grasp and then pop up behind them when he's huge as hell and smack the shit out of them). Unfortunately, that works pretty great in comics and cartoons, but I don't think it translates well to film.
He's also a very smart scientist, and actually is a pacifist that doesn't really like fighting. He created a prison for supervillains that's houses them in very tiny form (using the same methods he uses to shrink himself to ant size) making it easy to police. He, like Tony Stark, built robots to police them. One of them went rogue and became Ultron, a villain in its own right. Again, cool things in comic books and animated form, but probably terrible for film.
I love his character.