Apocalymon

Apocalymon is a massively powerful digimon that takes the form of a giant polyhedron, with a comparitively tiny humanoid being resembling Devimon coming from the top. Filled with dark thoughts, Apocalymon was born from the assimilated data of every Digimon that failed to evolve. 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. He knows all the evolutions and attacks of Digimon. In contrast to English version, the Japanese version had Apocalymon refer to himself in the plural sense. There are two possible reasons for this: he had no one to talk to but himself in his void-like dimension; 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 had been a plural entity.

Attacks

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

Digimon Adventure
Revealed to be reponsible for creating the chaos in the Digital World, 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.

The Adventurer's Battle
Apocalymon attempted to cross into the Real World to destroy it until he was confronted by Omnimon. But when he was seemingly killed by Omnimon, Apocalymon's data reformed into a new evil to carry out his justice. Its name was Mephistomon.

Digimon Adventure, Dub

 * I know who you are! You don't have the power to eliminate my sadness.
 * I am the ultimate evil, complete with hot and cold running water.
 * Are you repulsed by my appearence?
 * Don't be afraid to hurt my feelings. They're already hurt. You see, I was created from all that was lost during the digivolving process.
 * Digimon have been digivolving for many years now, over and over again. But there were some who weren't up to the challenge and simply disappeared.
 * Silence! Who's the one telling the story anyway, me or you?
 * First I have a question to ask. Do you believe that I am worthy of coexisting with you?
 * Oh really? Even though I was forged from the pain and misery of all the elvated Digimon who vanishing while attempting to digivolve.
 * Sure, rub it in. And now DigiDestined and Digimon. I have been waiting a eternity for this encounter.
 * As I sat alone in the cold misereble darkness on my world, I watched all of you on the other side, laughing and having fun in the light. Well now it's my turn, to SHINE!
 * Not for long! Do you think it's fair that I should have to live with all this agony? Why should you have to laugh while 'm forced to cry. Why do you get to taste the best life has to offer while all I do is choke on it's leftovers. Answer me this: Why do all of you get the pizza, while I get the crest.
 * I will rule the world and plunge it into darkness, so I don't have to be alone anymore in my misery.
 * Hahahaha, wait a minute what I'm laughing at? I'm supposed to be depressed.
 * That was MetalSedramon with his classic River of Power. And now here's Myotismon with this number one hit: Crimson Lightning!
 * Next: Machinedramon, Giga Cannon!
 * You fools, you haven't even see my true power yet!
 * I'll make you understand how it feels to be one step closer to extinction.
 * I hope you learned your lesson, always save your receits.
 * I'll take this children and use their fear to make them digital and disappear.
 * What!?
 * That's impossible! How did you digivolve without your crests?
 * They're doomed!
 * So you want a fight? Death Claw!
 * Let's end this! Virus Grenade!
 * Is that your best shot?
 * You think so? Well I may be beat, but I won't go down that easily. I'll take you and both worlds with me!
 * You still haven't seen my ultimate attack, TOTAL ANIHILATION!

Digimon Adventure, Original

 * Are we not worthy of being with others!? Answer us!
 * HAHAHAHAHA! Let all the light shines on be no more!
 * Ultimate Stream! That was a expression of our friendship. And now feel our love for you, Bloody Stream! And OUR sense of Justice, Infinity Cannon!