Red X's History
Robin
Red X was originally a cover identity that Robin had conceived as part of an attempt to get closer to Slade. Bent on stopping the threat that the madman presented by any means necessary, Robin approached Professor Chang for the necessary items - particularly Zynothium to use as a power source - to create the Red X suit and, posing as a ruthless master thief, Robin stole several computer chips that Slade was after and offered them with a proposition to forge a partnership between the two.
However, Robin's haste in trying to get too close somehow exposed his identity to Slade, and in fear that if he told his teammates about his plans, they wouldn't play their parts convincingly, he chose not to tell them. The plan eventually went awry: Slade revealed his knowledge of Robin's identity, and while Robin managed to retrieve the chips, Slade managed to elude him yet again. Robin was back at square one, with one additional step backwards: he had lost the trust of his friends.
Since the Zynothium power core could not be disposed of safely, Robin stored the suit inside a vault in Titans Tower, never to be used again.
The New Red X
Some time later, however, the suit was stolen from the vault by an unknown third-party who intended to use it for his own selfish agenda. Because the Zynothium Ore in the suit's power belt was nearly exhausted, Red X stole a handgun-like scanner which he could use to locate it. Not knowing where to look for him, and with Chang's supplier having been revealed to have skipped town, Robin "coerced" Professor Chang into revealing the most likely location where Red X could get his hands on more Zynothium: a highly-secured tech company at the city's south end which has a generous supply of Zynothium stored in their vault. Red X managed to penetrate the facility, with the Teen Titans (minus Cyborg) in hot pursuit, but Professor Chang's henchmen were following them, with Chang himself intending to swipe the Zynothium to power a gigantic disintegrator cannon of his own construction, and in an attempt to ensure no interference from Robin, he captured the other Titans and held them hostage.
Robin eventually confronted Red X and questioned him about his intentions for stealing the suit, his answer was that he was a thief, not a villain, causing Robin to realize he wasn't psychotic, just selfish. After being knocked out by Chang's henchmen, and subsequently captured by Robin, he confronted X about his self-serving attitudes, while Red X kept taunting Robin about the one mistake which helped create him. Unimpressed and willing to make amends, Robin went after Chang himself, but almost ended up his victim as well. At the last moment though, Red X saved Robin from certain death and aided him in freeing his teammates, including preventing Chang from attacking the Titans with his disintegrator, and eventually helped Robin bring him down. With Chang defeated, the Titans and Red X were back to being enemies. Red X attempted to abscond with enough Zynothium to last him for "quite a while", until Robin showed Red X that he had secretly swiped his power belt, rendering the Zynothium useless to him. Momentarily surprised by this revelation, Red X complimented him by saying "not bad, kid, not bad", then threw the Zynothium tube onto the ground to create a small explosion to act as a diversion for him to jump off the edge of a nearby cliff and quickly get away.
Later on, Red X was seen as a recruit among the ranks of the Brotherhood of Evil though it is unknown why he joined.
Eventually, with his power belt replaced, and somehow acquiring his own "X-Cycle", he participated in a race initiated by Ding Dong Daddy for a briefcase containing Robin's most prized possession. His intention was to sell it to the highest bidder. All throughout the race, he and Robin attacked one another, until a bomb dropped by Daddy blew him off the road, though he was saved by Robin at the last instant. Red X ungraciously remarked that "saving me was a mistake" but then asked if recovering the briefcase was really important to Robin. When Robin confirmed this, Red X told him to "go get it" and proceeded to use his teleportation system, agility, explosives and other gadgets to attack the other villains participating in the race and destroy their vehicles. His last target was a bus driven by Raven and Starfire, from which he withheld after recognizing them. He told the two girls to "Tell Robin we're even... For now", and disappeared.
Red X did not appear in the final confrontation between the Titans and the Brotherhood, implying he quit the organization. His current whereabouts and activities are unknown.