4. Scarecrow
First appearing in Tales of Suspense #51 in 1964, Marvel's Scarecrow (a blatant rip-off of DC's Batman rogue of the same name) is nowhere near as interesting a character as his DC counterpart, despite the obvious similarities. He first appeared while working as a contortionist in a circus, when he actually helped Iron Man to apprehend a criminal, but he decided to use his skills for criminal purposes in an attempt to get rich quickly after that, and came into conflict with a variety of heroes, notably Iron Man. In addition to his obvious athletic and acrobatic abilities, Scarecrow is also injected with a pheromone that gives him slightly superhuman strength and a healing factor (as well as the ability to inflict fear in others, like the character he is clearly based on). However, he also has the ability to control crows (oh dear), which he uses to carry out a variety of tasks, including attacking his victims en masse and killing them. On the off-chance that Marvel think "a Scarecrow character worked in the Dark Knight trilogy, why not in the Marvel Cinematic Universe?", they should quickly reconsider.