Traitor is a DC Comics supervillain to the Green Lantern Corps.
Traitor's true name is Devlos Ungol, and he was originally a warrior of great ferocity on his home world. He was eventually upgraded, merged with an armor that fed on the energy of dying stars and could adapt to any weapon thrown at it. However, he rejected his people, having concluded, during the agony he endured as the armor was fused to him, that there was no meaning in the universe besides pain and death.
With this philosophy in mind, Ungol crushed his people, who died calling him 'Traitor', assuming the name on a permanent basis. As he travelled, he gathered a vast army of pirates and survivors, until, at last, he fought the Green Lantern Starkaor, an early defender of Sector 2814. During the battle much of Traitor's armor was damaged, forcing him to retreat, but Starkaor was badly injured, and forced to appoint Abin Sur as his successor.
It took Sur several years to track Traitor down again, and in that time he had stationed himself on Earth in the late 1800s, forming an alliance with a criminal called Bloody Joe Tuscano until he could replenish his powers. Eventually, Sur arrived, but Traitor found what he believed to be the perfect weapon; gold-tipped bullets, their yellow color allowing them to injure Sur. However, Sur had formed an alliance with Marshall Henry Lee Jordan (coincidentally, an ancestor of Sur's future successor Hal Jordan), and Jordan was able to get Sur to a town where the bullets were removed, allowing the ring to heal him. The two of them subsequently fought off Bloody Joe and Traitor, Sur destroying Bloody Joe's weapons and Jordan distracting Traitor until Sur could imprison him in a pocket dimension in the ring.
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Official Site: D.C Comics
Links: Wikipedia Spider-Bob Un. Guide to D.C Universe