Yubel

Yubel is the villain of Season 3, an evil hermaphrodic Duel Monster whose card was in Jaden's possession when he was a little kid. For reasons not yet explained, Yubel became infatuated with Jaden, and harmed anyone who tried to harm or take him away from it, including putting Jaden's friend Osamu (who looks suspiciously like Kouyu Hibiki from the GX manga) in the hospital during a friendly duel. Because of this, Jaden was forced to send the card to KaibaCorp and have it shot into space, after which he completely blanked the whole ordeal out of his mind. After an indeterminate amount of time in isolation, Yubel's capsule returned to Earth, though the shock of reentry destroyed all but a single forearm of Yubel's body, which was eventually found by Professor Cobra. Tricking Cobra into helping it with the promise of restoring his adopted son Rick to life, Yubel coerced him into creating the Dis-Belts and Dis-Duels, absorbing the duel energy produced by them so it could reform its shattered body. This continued after Yubel transferred itself from Cobra to Martin Kanou, turning the students and faculty of the displaced Duel Academy into duel-obsessed zombies to help fuel its rebirth, and eventually securing the Sacred Beast cards to complete its reformation. In the end, during a duel between it, Jaden, and Johan, once it discarded Martin's body, Yubel was defeated by Johan's Rainbow Dragon card, and was presumed to be destroyed, though this can't be determined for sure.