19. Gorilla Grodd
Another less obvious villain, Gorilla Grodd is more famous for fighting the Flash. Part of the reason Grodd's on his list is because he's quite possibly one of the most ridiculously awesome villains ever. A super intelligent ape who wants to overthrow humanity as the dominant species on the planet. Mad scientist, war lord, and covered in hair. It's Planet of the Apes! Not to mention a holier-than-thou approach toward humanity, awesome inventions--just awesome. Gorilla Grodd's would probably be a doomsday villain, eradicating humanity so his ape army could rule supreme. This would be a huge departure from the Avengers, since the villains for the first two films are extraterrestrial. An earth based villain would be a welcomed change, especially one that's kind of primitive looking. There's just something appealing about seeing futuristic heroes going head to head with something old.