Source: dcau.wikia.com

5. Atomic Skull

That name is friggin’ magic, my dudes. ATOMIC. SKULL. If that name was any more metal, it’d make me involuntarily throw up the horns.

Atomic Skull started out life as the much more typically named Joseph Martin, a college student with a strange and undiagnosable medical condition. When Monarch attacked Metropolis, Martin accidentally stumbled upon an imprisoned Parasite. Monarch’s blasts hit both of them, and Martin started exhibiting clear signs of being irradiated. He lost his hair, he started to glow, he developed memory issues.

Martin was a fan of the Atomic Skull film serials, and in his irradiated daze, he began to imitate his speech patterns, eventually becoming convinced that he WAS the film serial character. When Superman inevitably showed up, he hallucinated that Supes was the villain from the serials and fought him.

Of course, Superman responded to this mentally ill man suffering from massive radiation poisoning by hitting him right in the face.