Orochimaru

Orochimaru's backstory reveals he was an orphan and a genius pupil of the Third Hokage, Hiruzen Sarutobi. His parents' death sparked a lifelong obsession with immortality and learning all jutsu. This pursuit led him to conduct unethical human experiments in Konohagakure (Hidden Leaf Village) and eventually defect, becoming a primary antagonist for much of the series. He later established his own village, Otogakure, and became known as one of the legendary Sannin alongside Jiraiya and Tsunade. Orphaned at a young age, Orochimaru became a student of Hiruzen Sarutobi, who considered him a prodigy seen only once in a generation. His teammates were Jiraiya and Tsunade, who together became known as the Legendary Sannin during the Second Shinobi World War. The death of his parents and witnessing the pain of loss (like Tsunade's brother and lover) presumably fueled his desire to cheat death and learn all the world's secrets. He found a white snake near his parents' grave, which inspired his research into forbidden techniques and rebirth. Orochimaru conducted extensive human experiments to develop techniques like the Cursed Seal and Living Corpse Reincarnation to achieve immortality. When his actions were discovered by Hiruzen, he fled the village to avoid persecution and became a wanted criminal. After multiple defeats and realizing the flaws in his approach through observing his former apprentice Sasuke Uchiha, Orochimaru eventually made peace with Konoha and became an anti-hero, focusing on research under supervision