10. Iron Man 2 - Whiplash / Justin Hammer
It should come as no surprise that the weakest film in the Marvel Cinematic Universe also has the weakest villain. To put it simply, Ivan Vanko, aka Whiplash, sucks. In Iron Man, we see Tony Stark go through painstaking efforts to build and perfect his suit. When he is finished, he has a war machine that is not only capable of flight, but also contains guns, missiles and blasters on his hands, feet, and chest. In Iron Man 2, Vanko uses the same technology to build...a whip. That's right, a whip. Why on Earth would you bring a whip to a fight with Iron Man? Granted, he didn't have the same resources as Tony, but then when he's given those resources by Justin Hammer, the film's secondary villain who is more comedic than menacing, he builds a suit with...another whip. Damn it Vanko! Look at what Hammer did for Rhodes' War Machine. Couldn't you have added more to your suit than a whip? Get some tank missiles on that thing, or some guns. Or, better yet, how about you don't plan your surprise attack for when the hero is already in his armor. Whiplash was an uninspired, boring, incredibly stupid villain, and easily the worst of the MCU so far.
Pros: He has a whip.
Cons: Poor planner, not very intelligent, every other weapon in the Marvel Cinematic Universe is better than his whip.