6. Mephisto is a class two demon from the Marvel Universe that exists to steal human souls and tempt superheroes (and their families) with power. As a demon, Mephisto has a vast array of inherent abilities like super strength, super speed, pyrokenesis (he can hurl fire at his enemies), dimensional entrapment, a regenerative ability, and immortality.
Mephisto is probably most known for taking Dr. Doom's mother to hell and for his role in Spider-Man: One More Day. In the book, Spider-Man makes a deal with Mephisto to save his Aunt May from dying... by sacrificing his marriage/life with Mary Jane. It's a truly dark moment in Spider-Man history.
5. Darkseid is a villain in the DC Universe and is one of Superman's greatest enemies. As a "New God", Darkseid is an immortal that wishes only to exterminate all life in the universe by finding the "anti- life equation".
Darkseid, born Uxas, achieves his immortality by usurping power from his brother, Drax. When Drax makes an attempt to claim the Omega Force, Uxas kills him and steals it for himself. The power of the Omega Force is what transforms Uxas into the rock-like creature known as Darkseid, and it is also responsible for his powers/immortality.
4. Sabretooth is a villain that I enjoy mostly because of the beating he gives Wolverine in Wolverine #10. Sabretooth has mutant abilities similar to that of Wolverine and spent years in the Weapon X program. Sabretooth's regenerative healing factor give him the appearance, and physicality, of a man in his prime despite his advancing age. There is little known about the specifics of such a healing factor and, as such, Sabretooth is considered to be immortal from natural death.
3. Vandal Savage is a villain in the DC Universe that obtained his powers and immortality, as a cave-man, when he was exposed to radiation from a crashed meteor. As time went on, Vandal developed into a menacing threat and known murderer. It is said that Vandal Savage was the inspiration for the biblical character of Cain- having committed the first known murder in human history.
It's funny to me that Vandal Savage is always depicted as a victorian gentlemen and never as an underdeveloped caveman. I guess once you've lived for 50,000 years or so.... you start to learn a little bit about class.
2. Ra's Al Ghul, Arabic for "the head of the demon", is a villain in the DC Universe who frequently battles Batman. Ra's Al Ghul is similar to Magneto in that readers often side with him because he is technically trying to fight for a good cause; he wants to restore balance to the environment of Earth by wiping out humanity.
Ra's Al Ghul makes this list due to his use of the Lazarus Pits to stay alive indefinitely.
1. The Joker is probably the most surprising character on this list, neh? In Batman #38 it is revealed that The Joker was exposed to the same radioactive meteorite as Vandal Savage years before Gotham even existed. This convenient retcon explains why The Joker is able to survive all of Batman's beatings and why he will always win.
It's also worth mentioning that Ra's Al Ghul's Lazarus Pits operate using residual radiation from the pre-historic meteor.