Kang's real name(in the comics) is Nathaniel Richards, he's the descendant of Reed Richards from Fantastic Four who resides in the 31st Century. Who knows if they change it for the MCU though. He's so powerful that the Avengers teamed up with Thanos to stop him at some point and Kang just kicked the crap out of them. Everything that has happened till this point in the MCU has only happened because Kang has allowed it to happen.