Thelonious Viper

Professor Thelonious Viper, known in Japan as Professor Cobra「プロフェッサー・コブラ」(Purofessā Kobura), is a professor hailing from West Academy and the main antagonist for the first arc of Yu-Gi-Oh! GX's third season. He was a former military commander who after losing his adopted son Pierce, allied with Yubel to revive him, using the Bio-Bands to drain energy from the academy's duelists. After failing to defeat Jaden Yuki, Yubel changes his memories and then leads him off a ledge, causing him to fall to his death.