3. The Master (Buffy The Vampire Slayer)
The Master was one of Buffy the Vampire Slayer's most formidable foes. In fact, he actually succeeded in killing her (though she was brought back to life). A centuries old vampire, the Master had totally lost his human face and possessed powers beyond those of most Buffyverse vampires, including superior speed, strength and durability to the likes of Angel, Spike, Darla and Drusilla, in addition to more esoteric powers such as psychic sensory and hypnosis, as well as various mystical abilities. Giving him a Black Lantern ring would put him far above anything Buffy ever encountered on the power scale and would make him a truly terrifying foe.