4. The Avengers - Loki / The Chitauri
Loki is unquestionably the best villain in the Marvel Cinematic Universe. He even gives Robert Downey Jr.'s Tony Stark a run for his money as the franchise's most beloved character. He's witty, confident, and ambitious, is capable of shape-shifting, illusion casting, and teleportation, has nearly conquered Earth, has successfully usurped the throne of Asgard, and has an amazing head of hair. So why is he only number 4 on our list? Because of his army. A great villain needs to have a great army, and Loki's Chitauri army is seriously lacking. From their lack of armor, to their flying jetskis that can't bank worth a damn, to their inability to survive once their mothership is destroyed, the Chitauri just don't hold up well compared to the other armies of the MCU. Heck, even Red Skull's Hydra had weapons that could disintegrate their enemies. The Chitauri's weapons are lame by comparison.
Pros: Come on, he's Loki.
Cons: The Chitauri aren't an army of Loki clones.