Aginor
During the War of Power, Aginor was a major asset to the Shadow. He was the leading figure in creating the Trollocs, Myrddraal, and gholam. He was proud of creating the Trollocs, for the skill in the Power that it took to make them, but was displeased that the Myrddraal were spawned from them. The other Forsaken became wary of him when the gholam were created though. The gholam were made to hunt down Aes Sedai, and they couldn't be harmed or touched by the Power, or any other weapon. The Forsaken didn't like things being made that they couldn't handle. Although there were only six made, at least one still survives now, and maybe more. Aginor tried to get an early shot at Rand, right after his release with Bathlamel. They met him at the Eye of the World, but were killed by him and Moraine, but not by balefire. Later, two Forsaken were reincarnated, and hints lead us to realize that Osan'gar is Aginor reincarnated. His current whereabouts are unknown, but he may be hiding in the Black Tower with Demandred.