Infinity War- A different Thanos

Thanos was the big bad villain of the MCU. Unlike in the Marvel universe we know however, Thanos was not a nihilistic despot with delusions of being a savior. In this version, Thanos is just as powerful, but a strange and mischievous prankster and frankly a pervert.

Thanos had been teased for a long time. He'd appeared in the end credit of the first Avengers film after a failed alien invasion attempted to destroy all inorganic material in New York. In Guardians of the Galaxy Thanos ordered Ronan to use an infinity stone to strip the entire planet of Xandar.

Well, now Thanos was done operating from the shadows. He was gathering the Infinity Stones. No one knew his exact intentions when he got all the stones, but they knew it wouldn't be good. So all the heroes of the MCU rushed to stop him, though Thanos was already so powerful their chances did not look good.