X-Men's Most Menacing Villain: Apocalypse

If there was anybody in X-Men that amazed me was Apocalypse. I tend to compare him to Mumm-Ra in Thunder Cats as both are over a thousand years old and are practically nearly immortal. So far, he had been around the world, menacing it. He had risen from the ashes of being left behind for his monstrous image, to being raised by Baal the Sand Raider to his rise to power, with the knowledge of sorcery and later technology. He had been the ultimate of destruction, seeking to make a world fit only for what he saw as fit. His true name was En Sabah Nur meaning the first light of the great dawn, which he believed himself to be.

So far, he had made a pact with the ancient spirits of evil to survive. He had over the years acquired several powers from ultra high tolerance to fatigue, being able to survive without food or water for a long period of time, enhanced strength, the ability to prevent aging and even fire dangerous blasts that could wipe out whole cities.  Later on, he found the Celestials' ship and used their technology. What he did not know was that he got more than he bargained for as the Celestials wouldn't take anyone using their technology so recklessly.

One of his greatest ordeals was to "evolve" man which had first replaced Angel's amputated wings with techno-organic ones and turned Angel into one of his horsemen. He was greatly awakened by Nathan Christopher Summers' birth, which he infected the child with the techno-virus, which he would see whether or not the child was fit enough to be his new host vessel. It was during the time he took over the Blue Area of the Moon where the Inhumans are currently residing.

He also was the author of "The Twelve" which he planned that twelve mutants are to be gathered, so he could assume higher power. However over the years, he could no longer hold his powers from within that he needed a new body. He through a series of manipulations gathered the Twelve which are Living Monolith, Storm, Sunfire, Iceman, Magneto, Polaris, Bishop, Mikhail Rasputin, Cyclops, Jean Grey, Cable and Professor X. He attempted to transfer their energies into Nate Grey, which in turn would be his new body.

However while attempting spirit transfer, Apocalypse was however stuck in Cyclops' body instead. He took advantage of whatever he can, created alternate timelines which he sought to correct the flaw in the plan. It turned out to be that from within, Cyclops was still alive and that bond allowed Jean Grey to separate him. Cable took advantage of the situation, used the Psimitar to apparently kill him. However he was able to preserve his essence, because as long as evil exists, he was frequently brought back to life which gave a disadvantage- he had to pay his debt to the Celestials too.

It was also perhaps, this characteristic that turned him into a boss character in the games X-Men vs. Street Fighter and Marvel Super Heroes vs. Street Fighter.