Holocaust

In the X men episode "one man's worth" the world is changed and and holocaust has a brief blink and you missed it cameo fighting alongside the x men!

Origin
William Rolfson, the son of Apocalypse and Famine in the Age of Apocalypse, grew up to be the evil mutant known as Nemesis. He was sent by his father to kill the X-Men and successfully killed a small group of young mutants and the Scarlet Witch. Enraged by the death of his daughter, Magneto hunted down Nemesis and destroyed his physical body, leaving his spiritual essence, which was then sent back to Apocalypse and put into the near indestructible armor that was made by the Dark Beast. And thus, Holocaust was born.

Power and Abilities
Holocaust's primary mutant power was the ability to absorb various forms of ambient energy, including the life energy of other beings, into himself. He could use this drained energy to augment his other mutant attributes and was fully sustained by these energies, therefore requiring no food, water, air, or even sleep to sustain his physical and mental health. By purposely channeling the energy he'd absorbed, Holocaust could grant himself superhuman strength sufficient enough to lift up to 2 tons. As a result of using his absorbed energy to enhance his strength, his musculature was far more efficient than that of an ordinary human. His muscles produced less fatigue toxins during physical activity than that of normal humans and he could potentially exert himself almost indefinitely, provided he could continue to absorb energy as needed.

Outside of his armor, Holocaust's body is in an almost intangible state. As a result, he is virtually impervious to all forms of physical injury. However, he must continuously absorb the life energies of others in order to maintain his form outside of his armor.

Holocaust could generate concentrated beams of plasma, which he often used in combat situations. At his peak, he could generate plasma blasts reaching a temperature of about 1,000,000 degrees Farenheit. He could also propel himself through the air, under his own power, at great speeds. He did so by creating super heated air currents that propelled him. While at his peak, he was able to reach speeds up to MACH-1, approximately 760 miles per hour.

Onslaught was able to alter Holocaust's brain engrams in order to render him resistant to most forms of telepathic assault. His engrams were altered to such a degree that he was rendered undetectable telepathically.

As Nemesis, Holocaust was also able to redirect energy into a negation effect on others' powers. Since losing his physical form, he no longer seems to possess this ability.