Yes, Thanos is the biggest, baddest villain in the MCU but he hasn’t done all that much yet. Hopefully he and his Infinity Stones will live up to the hype come Avengers: Infinity War.
Iron Man 3 adapted Iron Man’s nemesis with style, as Ben Kingsley was brilliantly cast. Sorry, what do you mean he isn’t the real Mandarin?! I have no idea what you’re talking about…
He might not be anything like the purple-hooded baron from the comics, but Civil War‘s take on Zemo was a fascinating master-manipulator who successfully tore the Avengers apart.
Kurt Russel’s power-hungry Living Planet was a brilliant addition to Guardians of the Galaxy Vol.2. He had a personal connection to Peter and was the most powerful villain the MCU has ever had.
Bucky might be on the road to redemption now, but he was certainly a villain in, er, The Winter Soldier. The conflict between him and Steve was one of the most dramatic in the MCU.
We really wish Red Skull had been used more up to this point, but Hugo Weaving’s portrayal in The First Avenger is enough to leap the disfigured Nazi up to fifth place.