Orochimaru

Orochimaru is an evil Sannin who killed the third Hokage, his sensei and took Sasuke under his wing in order to make him strong and thus steal his body. After the deaths of his parents, Orochimaru became obsessed in learning forbidden jutsu. While still in Konoha, he had an apprentice named Anko Mitarashi. He also conducted an experiment on the lives of sixty newborn infants, injecting them with Hashirama Senju's cells. He was once a member of the Akatsuki organization, partnered with Sasori.