Hawkeye

If there's one on-screen Avenger who looks significantly different from his comic counterpart, it's Hawkeye. For the big screen, Clint Barton dropped his garish pointy mask and uniform for a more tactical look. The two Marvel universes converged a bit in 2012, when Hawkeye's comic costume was redesigned to look more like the film's version, and less like a scaly, purple Wolverine. There's a reason we never saw that old-school mask on the big screen, either in Avengers or X-Men: it's ridiculous.

Both versions of Hawkeye are really good at shooting arrows, for whatever that's worth, and both are former agents of SHIELD. It's revealed that movie Hawkeye has maintained a secret family, while all comic book Hawkeye has maintained are romantic relationships with Black Widow and Mockingbird, a.k.a. Bobbi Morse. The latter appeared on Agents of SHIELD for awhile, but in a completely separate relationship, diverging the two universes once again.