Also tied for second place amongst the villains is the universally hated character of Vulcan.
The story of Polaris and Vulcan started long ago when Polaris sent Vulcan (and Darwin) into space as she lifted Krakoa with her magnetic powers whilst they were trapped on it in Giant Size X-Men #1 in 1975! However, the two had avoided seeing each other until Uncanny X-Men #485/6 when Polaris attacked Vulcan after he had killed Corsair- almost killing him as she forced his armour against his body and most likely violently affected the iron in his blood in his body with her mighty magnetic powers!! This was well appreciated by many Polaris fans- already upset at the length of Rise and Fall and blaming the character of Vulcan for her her space limbo in subsequent years.
Vulcan became Emperor Vulcan and in... 'X-Men: Emperor Vulcan' he captured and imprisoned Lorna and half of the Starjammers. Polaris was tortured, and her powers had to be repeatedly nullified during her capture as the side-effects of her powers as Pestilence seemed to render the drugs that were meant to suppress them ineffective. Polaris, though drugged, remained psychologically resilient and attacked Vulcan whenever she awoke (much to fans delight). Polaris was eventually freed and in the final battle of 'X-Men: Kingbreaker' hurt him once more.
Vulcan eventually (supposedly) died in the final battle of 'War of Kings'- much to Lorna's (and fans) relief! Unfortunately that did not spell the end of the space saga!