Thanos

He is the overarching antagonist of the MCU and main villain of Avengers: Endgame. He was behind most of the threats to the Marvel heroes and used to command the League of Villains, Giygas, Bowser, Porky Minch, and many more evildoers. He also has a dinosaur named after him.

Appearance
Thanos looks like an unnaturally tall and muscular purple boi. He has a huge chin that takes up almost 1/3 of his face and it's covered with lines for some reason. Most of the time he wears golden armor, but the Avengers caught him in sweatpants and a white t-shirt shortly before killing him.

Story
Thanos doesn't come into play until Avengers: Infinity War, where he teams up with Porky Minch and the League of Villains to wipe out half the Universe with the Infinity Stones. After that his head gets chopped off by Kumatora, he is accidentally brought from the past to 2022 where Deku sacrifices himself to destroy Thanos and his army.