Rick is the protagonist. There is, for example, 30 minutes in the conclusion when Supernova is kind of villain-ish, but Rick is the bad guy here; he gets drunk out and blacks, and while he is blacked out he constructs an elaborate collection of Jigsaw-like cubes to punish the superhero band which Morty is now infatuated with. His traps kill two members of this team, also tensions between the natives get the remaining part of the task done. So frankly, even as a villain he’s kind of half-assed. That’s, of course, the purpose.