Kang

Kang is a conqueror from 41st century who opposes the Avengers.

The Avengers: Earth's Mightiest Heroes
Kang finds out his timeline is being erased, so he travels with his troops in the Damocles base to the present day to destroy Captain America, who seems to be the cause by surviving his apparent death in World War Two. Right before the time jump, Kang's wife Ravonna is trapped by the erasing effect but saved by Kang, which leaves her in an intermediate existence state.

Kang faces the Avengers, who refuse to turn Cap to him. After a fight, he returns to Damocles and sends an invasion force to take Earth. The Avengers defeat part of this force ant then find Damocles, where they face and defeat Kang, who is defeated and jailed. Henry Pym and Reed Richards take care of Ravonna to find a way to save her.

Hulk and the Agents of S.M.A.S.H.
When Hulk and Rick Jones see the Negative Zone portal, Rick mentions Kang as one of the villains who could have caused it.