2. Bizarro
Created by Lex Luthor in an attempt to clone Superman, the inception of Bizarro comes from a test tube. Now by no means is he the smartest of villains but as Superman's opposite, he's just as strong and poses as great of a threat as anybody. Not only is Bizarro as strong as The Man of Steel but he can also breath fire, fly and has freeze vision. Bizarro isn't always portrayed as Superman's antagonist but with his lack of intellect, he often finds himself as a manipulative pawn of other super villains who use him to fight their battles.
How would you introduce him in the movie? What would make the most sense is for him to appear in a movie with Lex Luthor. As his creator, Lex would convince Bizarro that Superman is a menace and needs to be destroyed. Bizarro, easily manipulated, would believe Luthor and attack Superman with full force. With a battle similar to the one with General Zod, it'd be a war of powers colliding, destroying everything in their path. Metropolis would be in ruins. Ruins in which Lex would happily pick up the pieces to and claim as his own as Metropolis's greatest antagonist.