Vali (Ramayana)
In Hindu mythology, Vali was the monkey-King of Kishkindha, a son of Indra and the elder 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 in his back. At first, Rama was troubled by the performance of this dishonorable deed, but was later persuaded by Sugriva that it had been right. Vali had been known as a good and pious monkey-king, but had been too arrogant to listen to Sugriva after his brother had accidentally sealed the entrance to a cave in which Vali was fighting a demon. Thus, when Vali had emerged, he'd found that the entrance to the cave was blocked (not a problem for his strength), and had then discovered Sugriva ruling in his place. Sugriva had thought that Vali was dead, and so had ruled in his stead, but though he'd tried to explain the situation to Vali, Vali would not listen, and had him driven out of the kingdom.