Apolyon is a villain from Chaos! comics, first appearing in Chaos! Quarterly #3, and later serving as a major antagonist in the Cremator miniseries.
Apolyon was an Angel in God's employ, who worked with Him for billions of years before he was banished from heaven. Apolyon had, apparently, discovered the truth behind Hell's purpose: it existed only to make Heaven seem good.
Upon leaving Heaven, Apolyon tried to join his former friends; Asmodeus, Mephistopheles, and Belial . While they initially offered Apolyon hospitality, they would eventually sell him out to Lucifer. The five of them were implied to have engaged in a heavy battle before Apolyon was defeated.
After his defeat, Apolyon was left alive (as Angels are, by most causes, immortal) and subsequently subject to torture at the hands of the Trinity and the Devil. Realizing that he could eventually break free and seek revenge, Lucifer commissioned Cremator to build a prison for Apolyon.
400 years later, the Trinity of Evil had removed Lady Death from Hell and attempted to conquer it. Cremator opened Apolyon's prison, knowing that he was the only one who could defeat the Trinity. Upon being released, Apolyon, surprisingly, didn't kill the blacksmith on the spot. He instead went on a quest to kill the Trinity, and eventually all of Hell, as that would unravel all of creation.
Apolyon engaged in a battle with the Trinity, creating Cosmic levels of destruction before Cremator attacked the Trinity with the Spear of Destiny. Apolyon managed to Kill Mephistopheles, but was then killed by the combined efforts of Belial and Cremator.
As an angel, Apolyon commands massive power (said to be comparable to that of Lucifer). He can even disintegrate entire planets without showing any signs of stress or fatigue.