Sinedd: Primary antagonist for seasons 1 and 2, is a human who plays for an alien team, massive jerk, gets involved in illegal underground football with no rules against injuries.
Artegor: Coach of above-mentioned alien team, tries to steal players off human team, lets human player use alien ability even though it made him sick/ended his career, secondary antagonist.
Season 2 Rocket: Gets kicked off human team, starts playing underground football, somehow that turns him evil and makes him break another player's ankle and not care about it, and also nearly demolishes his girlfriend? Honestly, I've never really understood that plotline though I've loved it, evil Rocket is just so much better than normal Rocket.
Galactik Football
Artegor: Coach of above-mentioned alien team, tries to steal players off human team, lets human player use alien ability even though it made him sick/ended his career, secondary antagonist.
Season 2 Rocket: Gets kicked off human team, starts playing underground football, somehow that turns him evil and makes him break another player's ankle and not care about it, and also nearly demolishes his girlfriend? Honestly, I've never really understood that plotline though I've loved it, evil Rocket is just so much better than normal Rocket.