In the comics, he was an exiled Wakandan who returns to exact his revenge on Black Panther.
Early reactions to the film praise Killmonger as one of the best villains Marvel has ever done.
His exact goals in the movie are still unknown but he does get his own vibranium Black Panther suit so he can go toe-to-toe with T’Challa.
Erik Killmonger (Michael B. Jordan) is the main antagonist of the movie and he seeks to usurp the throne in order take control of Wakanda for what he sees as the “greater good,” which likely doesn’t mean anything good for the rest of the world.