Homelander (real name John Gillman) is the main antagonist of the comic book series The Boys, and one of the two posthumous overarching antagonists (alongside Black Noir) of it's sequel/spin-off miniseries The Boys: Dear Becky.
He is also the leader of The Seven, one of the strongest Supes in the world, and the archenemy of Billy Butcher, the leader of The Boys.
Homelander is basically a psychopathic parody of Superman.