Apocalymon

Apocalymon is a massively powerful Digimon. Apocalymon's arrival was written down in ancient prophecies and the hatred of the Digimon that formed him lingered on. A sadistic and tormented soul, Apocalymon wanted to make the Digital World a living hell to justify the darkness that composes him.

In contrast to English version, the Japanese version had Apocalymon refer to himself in the plural sense. There are two possible reasons for this:
 * 1) He had no one to talk to but himself in his void-like dimension
 * 2) Or as a reference to the demon Legion who was also composed of many. Thus from the 2nd reason, Apocalymon, as a being assembled from the data of thousands if not millions of Digimon, may truly have been a plural entity.

Description
Apocalymon takes the form of a giant polyhedron, with a comparatively tiny humanoid being resembling Devimon and Myotismon coming from the top. Filled with dark thoughts, he was born from the assimilated data of every Digimon that failed to Digivolve. He knows all the evolutions and attacks of Digimon.

Digivolution
Apocalymon was never given a precise evolution line in the anime. In the card and video games, however, he may evolve from MetalSeadramon, Puppetmon, Machinedramon, Piedmon.

Attacks

 * Total Annihilation (Grand Death Big Bang): Suicide attack that produces an explosion strong enough to wipe out an entire dimesion. Used as a final resort.
 * Virus Grenade: Launches laser grenades at his opponents.
 * Darkness Zone: Reverts his enemies to nothingness.
 * Reverse Digivolve (Death Evolution): Reverts Digimon.
 * Copied attacks: The giant claws morph to enable Apocalymon to use the attacks of others.
 * Giga Cannon (Mugen Cannon): Machinedramon's attack.
 * River of Power (Ultimate Stream): MetalSeadramon's attack.
 * Crimson Lightning (Bloody Stream): Myotismon's attack.
 * Death Claw: Devimon's attack. Can send a lot of Devimon arms to seize opponents.

Digimon Adventure
Revealed to be responsible for creating the chaos in the Digital World and creating the Dark Masters, Apocalymon appeared to destroy the DigiDestined with his powers. He destroyed the Tags and Crests and sent the DigiDestined to the Data World before they returned using the "Crest" power that was within them all along. It took a combined force of WarGreymon, MetalGarurumon, Garudamon, MegaKabuterimon, Lillymon, Zudomon, MagnaAngemon and Angewomon to even begin to harm him; during their battle they managed to destroy the humanoid portion of him. However, as he explained, the humanoid form was only a part of him, albeit an important one. A dying Apocalymon then attempted to take the DigiDestined down with him using his ultimate attack, Total Annihilation. However, the Digivices of the Digi-destined contained and negated this kamikaze attack.

Digimon Tamers
What might be Apocalymon was among the shadowed Digimon that wanted Rika to tame one of them.

Battle of Adventurers
Apocalymon attempted to cross into the Real World to destroy it until he was confronted by Omnimon. He broke apart from his polyhedral body, his core reforming into a Mephistomon. When Mephistomon was seemingly killed by Omnimon, he in fact escaped to the Tamers world.

Digimon World 4
Apocalymon is seen at the end of his base which is at the end of Numenume River as the final boss in Death Valley.