In Hinduism, Vali is the monkey-King of Kishkindha and a son of Indra and brother of Sugriva. He was killed by Rama, an avatar of Vishnu.
He was famous for the boon that he had received according to which anyone who came before him lost half his strength to Vali thereby making Vali invulnerable to any enemy. Hence Rama slew him with an arrow from his back.