Apocalymon & Its Creation In Digimon Adventure

Apocalymon is the strongest Digimon in Digimon Adventure story. His existence generates chaos in the Digital World and in space-time itself, particularly the creation of 4 Dark Masters. Before the DigiDestined ever arrive in the Digital World, Apocalymon also created Devimon, along with his successors, Etemon and Myotismon. Below is the description of him and his creation:

Apocalymon (Mega) 

Apocalymon is an Unidentified Digimon. It is a Digimon who appeared when negative thoughts were drawn together by darkness. So little is known about Apocalymon that it may not even be a Digimon. Some claim it appeared to purge the chaos of cyberspace, and reduce it back to nothing; others claim its arrival was spoken of in ancient texts.
Attacks
Darkness Zone: Calls forth an infinite darkness. Anyone or anything caught in its wake is said to be consumed by the void and eventually reduced to nothing.
Reverse Digivolve: Captures the opponent in its claws and forces them to degenerate.
Total Annihilation: Detonates its own body with enough force to wipe out an entire dimension.
Shokushu Kougeki: Does a physical attack with its tentacle claws.
Death Claw: Attacks using its claws.
Copied Attacks

• River of Power: Transforms a claw into MetalSeadramon's head, which fires its River of Power. This technique symbolizes Apocalymon's "Friendship".
• Crimson Lightning: Transforms a claw into Myotismon's upper body, which attacks with its Crimson Lightning. This technique symbolizes Apocalymon's "Love".
• Giga Cannon: Transforms a claw into Machinedramon's upper body, which attacks with its Giga Cannon. This technique symbolizes Apocalymon's "Justice".
• Death Claw: Transforms a claw into Devimon's arms, which attack with its The Touch of Evil.
• Virus Grenades: Fires Datamon's Virus Grenades from every opening.

Piedmon (Mega) 

Piedmon is a Wizard Digimon. It is a strange-looking and elusive Digimon that is completely shrouded in mystery. Demon Man Digimon have many mysterious qualities, and since Demon- and Undead-species are basically beings from another dimension, their true identities are totally misunderstood. It is unclear why Piedmon appeared and what the purpose of its existence is, and there are currently no means of clarifying these questions. However, since its strength is without equal, if you happen to stumble across Piedmon, you probably won't be able to do anything but curse your fate. It has four swords pierced through the "Magic Box" on its back.
Attacks
Trump Sword: Teleports its four swords, causing them to skewer the opponent in the following instant.
Clown Trick: Does various magical effects including transformations, disguises, or reflecting an opponent's attack back.
Masks Square: Creates a field in which all communications can be read by it and allows it to teleport itself and its attacks anywhere at will.
Toy Wonderness: Creates a gust of wind.
Ending Snipe: Unleashes electricity from both hands and electrocutes opponents.

Machinedramon (Mega) 

Machinedramon is a Machine Digimon. With its whole body in 100% full metal, it is the Digital World's strongest Digimon. It was built by synthesizing the parts of many Cyborg Digimon, and it is thought that all of the Cyborg Digimon produced so far were merely prototypes for the completion of Machinedramon. Its power is at a level that would overwhelm other Digimon, and it possesses an intellect which boasts incomparable throughput, but it is a purely mechanical Digimon which does not share their self-will. Instead, someone planted a program containing evil intentions within the DigiCore at the center of its body, and Machinedramon is supplied with infinite power from that malice-filled DigiCore.
Attacks
Giga Cannon: Fires superdreadnought-class energy waves from its two cannons.
Dragon Fire: Drills its right arm into the opponent.
Catastrophe Day: Detonates itself in a large explosion.
Infinite Hand: Launches a blast of energy from its hand.

Puppetmon (Mega) 

Puppetmon is a Puppet Digimon. It was built from the body of a cursed Cherrymon, and it is thought that it was probably constructed from Cherrymon's data by a single fiendish hacker. It has an appearance like a marionette, but it can move under its own volition. Its personality is detestable, as it tells fibs, and when a computer presents false information, it is the work of Puppetmon.
Attacks
Bullet Hammer: Packs gunpowder into its revolver-style hammer, then strikes with its strongest technique. This attack will cause the opponent to vanish without a trace, not just from the hammer's blow but also from the explosion of the gunpowder.
Flying Cross Cutter: Throws the wooden cross on its back like a sharp boomerang.
Lie: Tells multiple lies to make its nose grow and hit the opponent with it.
Drill Nose: Spins its metallic nose like a drill. 

Kyoudai Mokujin: Creates a big man in the form of a house

MetalSeadramon (Mega) 

MetalSeadramon is an Android Digimon. It is the final form of the Seadramon-species whose whole body is covered in the strongest metal, Chrondigizoit alloy. Its Metal Body reflects every attack. Furthermore, it has the fastest speed of movement among aquatic Digimon. MetalSeadramon was remodeled as a Digimon for use in interception under the sea. Through this, it was completed as a Digimon for use in land, sea, and sky interception.
Attacks
River of Power: Fires an energy cannon from its snout.
Hot Squeeze: Powerfully constricts its enemy in its coils.
Poseidon's Divide: Summons up a tsunami and directs it at the foe.
Shimetsuke: Squeezes an enemy with its body.

Myotismon (Ultimate)

Myotismon is a Ghost Digimon. As the king of Ghost Digimon, it was resurrected through the dark arts and obtained mighty powers. Originally a fiendish computer virus which destroyed the computer data it absorbed, it possessed the ability to revive the destroyed data as malignant computer viruses. As it possesses an extremely cruel and cunning personality, it is exceedingly difficult to destroy this Digimon. However, it cannot demonstrate its powers outside of the night, and its power is cut in half during the daytime.
Attacks
Grisly Wing: Manipulates a countless swarm of bats, and begins a surprise attack.
Crimson Lightning: Uses a stream of blood like a whip.
Blood Punch: Continuous strikes using both hands.
Nightmare Claw: Sends out a black, ghost-like entity that turns the victim black and paralyzes them.
Nightmare Wave: Uses a special radio wave to lure the enemy to sleep.

Etemon (Ultimate)

Etemon is a Puppet Digimon. It is an unidentified Digimon that suddenly appeared in the Digital World. It calls itself the "King of Digimon", and its fighting strength is beyond imagination. And, well, it's rumored that it pulls the strings of the mysterious Digimon "Monzaemon". It is dressed in its reinforced "Monkey Suit" which can endure every attack, and even today, it bustles about the whole world for the sake of its unending battles. It is a close rival of Volcamon.
Attacks
Concert Crush: Breaks the opponent's heart and makes their fighting spirit vanish.
Dark Network: Attacks with a dark sphere that consumes everything it touches.
Monkey Kick: Attacks with a strong hard kick.
Dark Musical: Sings a song that is totally off-key.

Devimon (Champion)

Devimon is an Evil Digimon. Its body is clad in jet-black cloth. Although it was originally a shining Angemon-species Digimon, it was lured to the Dark Side by DemiDevimon and fell to the Dark Area, becoming a fallen angel. As proof of that, the Mark of Evil surfaced dramatically on its chest. It has a cunning and fiendish personality, but it also possesses an outstanding intellect. It is said that those who have stared into its two eyes, which shine a deep crimson, are mind-controlled and completely dominated by Devimon's mind. Although it has the same outward appearance and Special Move as the Devimon that inhabit File Island, it seems its lethal potential and power are remarkably increased.
Attack
The Touch of Evil: Extends both of its extensible, elongated arms even further, and enforces its will on the opponent's body.
Laser Wing: Flaps its wings to fire destructive energy from them, summon a dark tornado, or crush enemies with air pressure.
Dungeon Curse: Sends a cloud of cursed Digimoji at the enemy or summons up a cursed contract to confuse them.
Death Hand: Unleashes a blast of unholy energy from hands.
Deadly Nail: Scratches using the nails on both hands.