sauron (meaning lord of abomination)
well sauron was not defeated as soon as the ring was cut off, that was only in the films, in the books that was the last blow to him. with the gold of the ring he mixed his own blood, they are one sauron and the ring. he is a maiar of aule nurtured to darkness by melkor, a.k.a morgoth he was morgoths most trusted servant and his leiutenant. he was defeated by huan when sauron did battle with huan as wolf-sauron after that he disapeared and took no active part in the war of wrath and did not re-emerge until the second age, as Lord of Gifts Annatar, the tempter of the M铆rdain, then after he was defeated by isildur he left for a while and returned as the necromancer (normal meaning a spirit with power over the dead, but tolkien was leaning more to black magician) he evil being who dwelt at Dol Guldur in the heart of Mirkwood; originally thought by the Wise to be one of the Nazg没l, Gandalf later discovered that the Necromancer was Sauron himself.