Parasite could be very cool for a first film villain. As others have said, he would be visually interesting and wouldn’t just be another case of the villain just being an evil version of the hero. He’s also small scale enough that he couldn’t be topped by Brainiac or whoever they might use in a sequel.
I would still hope though that the movie at least alludes to Brainiac, either in a cameo or some type of reference to let fans know that he’s coming.
Parasite would be fun, definitely. And you can easily partner him with Luthor and/or another supervillain. The appeal is the power set—Rudy Jones has had so many different origins every time he’s adapted on page or screen; I really think Gunn has carte blanche, frankly, for a lot of Superman’s rogues.
Having just read Grant Morrison’s first Action Comics story arc, I think
Superman and the Metal Men could be an interesting story to tackle for a young Superman film. It’s Superman in a protosuit facing against the likes of organized crime, Lex Luthor, Metallo, and Brainiac (though he’s more of an Act III reveal).
Essentially, the story takes place 6 months after the first appearance of Superman—Lois has already written her expose (“faster than a speeding bullet, etc.”) and the world is trying to figure out to live in a world with a Superman.
At this point, Superman is operating as a vigilante of sorts, protecting the downtrodden that he writes about in his pieces for the
Daily Star. The story opens with him targeting corrupt businessman Glen Glenmorgan (though I think I’d replace him in a film adaptation with Bruno Mannheim or Morgan Edge).
General Sam Lane turns to Luthor to capture Superman. Luthor has access to Superman’s original rocket ship, and is secretly communicating with an unknown source that is providing him information about Superman’s Kryptonian origin.
Meanwhile, the army is developing a project headed by Dr. John Irons to create super mech soldiers, Project Metallo. Sgt. John Corben has trained for the last 5 years to pilot the exo-suit.
After preventing a a high-speed monorail crash (orchestrated by Luthor), Superman is in US Military custody and studied. He eventually breaks out and reclaims his rocket ship.
Seeing Superman square off against the military, Corben decides to jumpstart Project Metallo. As he integrates with the Metallo suit, his mind is corrupted by Luthor’s unknown benefactor—Brainiac.
Superman and Steel square off against a mind-controlled Metallo and an army of sentient Metal Men to stave off Brainiac’s invasion of Earth.