I know people are going to freak out about this so may as well discuss it. Not that I put a whole lot of stake in an anonymous Reddit post, but if ti's true that Zac Efron is being considered for the role, I don't think it's necessarily a bad thing.
First let me say, with his chiseled looks and perfect hair, I can actually see him in the role especially with Gunn's interpretation of the Soverign. Secondly, humor wise, I could totally see him fitting in James Gunn's universe. This is going to be an interpretation of the character, not the dead serious one that we see in the comics, but one that fits into the MCU Guardian's universe. Seeing his performance in neighbors, Zac can be extremely funny.
Finally Zac has consistently tried to break out of the High School Musical role since he left it. The guy is a talented performer so we shouldn't hold it against him that he got his start as a Disney star, or that he was in a teeny bopper film over 12 years ago. I haven't seen the film, but anyone that would attempt to play Ted Bundy in a film, is someone who is a serious actor and not afraid to stretch out.
Again, I don't want to give too much credence to this, but it's hitting the news now, and I think that we should have a little faith in the film makers if this happens to be a serious discussion on casting him.