John Corben


 * For his partner in the role of Metallo, see Gilcrist.

"John Corben dies today. Long live Metallo."

- Lillian Luthor

John Corben was an international assassin-for-hire. He was hired by Lex Luthor to kill his adoptive sister Lena, but in doing so was nearly fatally shot. Corben was subsequently saved by Project Cadmus and turned into a Kryptonite-powered cyborg known as Metallo.

Early life
John Corben had links to Intergang, Kasnian terrorists and a genocide that occurred in Corto Maltese.

Attempted assassination of Lena Luthor
Corben was hired by Lex Luthor, who was in maximum security prison, to assassinate his adoptive sister, Lena Luthor. He began by tampering with the oscillator of the Venture space craft, which would be located directly beneath Lena. However, after she couldn't make it due to an important business meeting, subsequently missing the explosion of the craft, Corben had to use an alternate plan to kill her. He took a Heavy Tactical Unmanned Air Vehicle from Baker, using it to target Lena's helicopter, while planting additional drones throughout National City to shoot random civilians; Superman and Supergirl ultimately destroyed all of them, saving Lena. The following day, he planted explosives beneath a plaque at Luthor's ceremony to rename her company. They detonated, along with others planted in the Luthor Corp building. Corben, dressed as a police officer, attempted to approach Lena directly but was intercepted by Alex Danvers. After a brief fight, he took her hostage, threatening to shoot her if Supergirl intervened. He was promptly shot from behind by Lena Luthor, dropping Alex. Sometime later, John found himself connected to medical equipment inside Project Cadmus. A woman approached him, offering to let him live, to which he agreed, and he was injected with something, causing his veins to glow and his eyes to cloud over. The woman dubbed him "Metallo".

Working for Cadmus
After becoming Metallo, Corben initially awoke confused at his newfound strength. When asked who his captor was, the woman responded that she was "merely a Doctor". She introduced him to Cadmus and explained their anti-alien mission, which he hastily sympathized with. He was then dispatched on a mission to kill Supergirl and Superman.

Disguised as a suicidal man on a bridge, he attracted the attention of the Kryptonians who he swiftly defeated, rendering Supergirl unconscious, however he was knocked away by Superman before he could kill her. After converting Gilcrist into the "Metallo" state similar to Corben's, Cadmus sent them on a mission, during which, Corben drew Superman and Supergirl's attention to himself, while Gilcrist terrorized Metropolis. Corben later challenged Supergirl, who teamed up with Alex Danvers and removed his "Kryptonian heart". Supergirl then spoke through Corben's eyes to Cadmus that she will find them.

Breaking Lillian Luthor out of prison
As Lillian Luthor's trial was impending, Metallo managed to get a new Kryptonite heart from Hank Henshaw and used it to free both himself and Lillian Luthor, he drew Supergirl back to keep her from stopping them. Later, after Lena was arrested for being a suspect in aiding in their escape, Metallo was sent by Lillian to break her out of prison too, in doing so he was confronted by Guardian, which he managed to quickly subdue. Metallo brought Lena to Lillian, who later took them both to a vault created by Lex in which Henshaw was waiting them.

The Luthors opened Lex Luthor’s mountain vault, before Supergirl arrived having following the radiation of Metallo's new Kryptonite heart which, being synthetic, unknowingly to him is slowly killing him. After a harsh fight between him and Supergirl, aided by the Martian Manhunter, despite the heroine tried to convince him of the new Kryptonite's decaying properties, Metallo refused to listen and continued to fight her using his Kryptonite beam, making his body more and more unstable until his eventual explosion.

Powers

 * Cyborg physiology: Through an operation performed by Cadmus doctors, John became a cyborg and the cyborg physiology grants him special powers and abilities.
 * Enhanced strength: As a cyborg, John's strength was apparently able to match that of a Kryptonian, however, it should be noted that Superman and Supergirl were weakened by his green energy beam of Kryptonite at the time, in their rematch, Kara who now had an anti-kryptonite suit and at full strength, was able to overpower John easily.
 * Enhanced durability: As a cyborg, Corben can take much more damage than a normal human; he took physical blows from Supergirl and Alex (in a Kryptonite-powered exosuit) remaining relatively unfazed.
 * Enhanced stamina: As a cyborg, John's natural stamina levels have been increased considerably, allowing him to fight and remain active for long periods of time without becoming fatigued.
 * Kryptonite beam: John was able to fire a green energy beam of Kryptonite radiation. A sustained blast has shown to cause extreme pain to Supergirl.

Abilities

 * Expert assassin: Working as an assassin-for-hire, Corben was an expert at his profession, having been hired by terrorists and businessman alike.
 * Expert hand-to-hand combatant: Corben had been shown to be able to defeat D.E.O. agent Alex Danvers. He was also able to best James Olsen who is a capable fighter.

Weaknesses

 * Synthetic Kryptonite: While this new Synthetic Kryptonite in Metallo's heart is the source of his power, it is the source of his downfall. The new Kryptonite's decaying properties in a modified human will slowly kill him as time passes by. However, the more Corben uses the Kryptonite beam, the faster it will decay, making his body more and more unstable. This will go on for some time until eventually, he explodes.