In Norse mythology, Vali was a child born of Odin and Rind, a giantess. He was birthed for the sole purpose of killing Hod as revenge for Hod's accidental murder of his brother, Baldur. He succeeded.
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.