Hanzō

"Salamander" Hanzo is a legendary ninja from the time of the great ninja wars. Little is known of his abilities aside from his riding on the head of a giant salamander (presumably a summon), but he was so powerful that he with his summon fought off all three Sannin. After their battle, he was so impressed with their strength that he decided to leave them if they agreed to accept the title of Sannin ("The three legendary ninjas"). He was later single-handedly defeated by Pein, despite the backing of Amegakure. Every person that he was ever connected to was systematically killed, and at this point there is nobody left.