SINISTER

SINISTER is a fascist group that repeatedly destroys the entire universe a ton of times

Casimir is the leader

Ragnor is the one notable guy for basically being Casimir's right-hand man guy thing idk

oh yeah they stole Q.E.D. from Quill for their world domination schemes

I'd say that they're the main antagonist of the series but eh there are some other candidates

also both ragnor and casimir were killed in the endgame by eric so SINISTER basically collapsed