Mirroring Malevolent Metallic Menaces

While not as infamous as Roger “Metallo” Corbin of Earth-One and “ George “Metallo” Grant of Earth-Two, there was another pair of cyborg crooks who briefly made names for themselves. Unethical reporter John Corbin and an unidentified criminal were one-time pests of the Men of Steel, rivaling these superhero's powers due to their mechanical bodies 

On Earth-One, Corbin was inadvertently the victim of a near-fatal automobile accident, which very nearly claimed his life were it not for the timely intervention of Professor Vale. The scientist used his robotics research to reconstruct John's damaged body with a robotic facsimile which was powered by a radioactive Uranium heart. Due to the expenditure of this synthetic heart to keep Corbin alive, it had to be replenished every day. As Metallo, Corbin proceeded to use his new found powers to steal Uranium to reignite his life-sustaining mechanical organ. Simultaneously, he was hired a reporter for the Daily Planet, where he fell in love with Lois Lane.

On Earth-Two, an escaped criminal nearly perished from a plane crash, with only his brain surviving as his human body was crushed. Roboticist Dr. Manfred Zanger had built a prototype mechanoid, based on Dr. Robert Crane's own Robotman creation which Crane's brain now resided within. Seeking to see if his research would bore fruit, Zanger implanted the fallen felon's brain within his robot. However, when this this new metal man gained consciousness, he recalled his previous life... and sought to use his new body to avenge himself on his former enemies.

Vale eventually discovered that Kryptonite could power Corbin's heart, and gave him a small fragment he possessed. Seeking a larger piece of Kryptonite to both indefinitely power his Metallo body, as well as kill Superman who was challenging him, Corbin was lured to an exhibit where a large Kryptonite fragment was on display. While disguised as Superman, Corbin stole the meteorite and threatened Lois' life, as she was uncovering the truth about Metallo's secret identity. In fact, the meteorite he placed in his chest was a fake, and without its radioactive energy, Corbin perished. However, his brother Roger would seek revenge against Superman, and would become the second Metallo.

Robotman pursued this new Robot-Criminal, attempting to lure the rogue into a body of water, theorizing that the metallic menace hadn't mastered the ability to swim underwater. However, Robot-Criminal's framework allowed his brain to carry oxygen in reserve, preventing him from drowning. On their next encounter, Robotman tricked onto a railroad rack, whereby Robot-Criminal crapped an electrified hird rail. The surging electricity presumably had fatal effects on Robot-Criminal's brain, with his now lifeless body collapsing and no longer a threat. Still, George Grant proved an even greater menace as Superman’s foe Metalo.