What he did: Infected innoucent Digimon with Black Gears to turn them evil. Tried to take over the Digital World.
Attacks: Touvch of Evil
What happened to him: Patamon Digivolved for the first time to Angemon and used all his power to kill him.
What he did: Etemon attacked Digimon with his Dark Network. He thought he was better than everyone else.
Attacks: Dark Network and Concert Crush
What happened to him: Agumon Digivolved to his Ultimate level, MetalGreymon, for the first time, to beat him. He returned later as MetalEtemon, but Zudomon, with SaberLeomon's sacrafice, killed him.
What he did: Killed innocent Digimon. Tried to take over the Digital World and the real world.
Attacks: Crimson Lightning and Grisly Wing
What happened to him: Angewomon "killed" him, but he really got stronger. He came back as VenomMyotismon. (show here)
Then WarGreymon and MetalGarurumon destroyed him. Yet, he came back in season two as MaloMyotismon, but the infected children's dreams destroyed him.
>-The Dark Masters-<
What he did: He killed Whamon. He controlled the water.
Attacks: River of Power and Giga Ice Blast
What happened to him: WarGreymon ripped him to shreds.
What he did: Didn't have any friends, so he kidnapped T.K.
Attacks: Puppet Pummel
What happened to him: MetalGarurumon appeared. Puppetmon tried to attack him but it didn't work. MetalGarurumon killed him.
What he did: Attacked the Digidestined.
Attacks: Dragon Fire and Giga Cannon
What happened to him: WarGreymon sliced through him.
What he did: Trashed the Digi World. Tried to kill the Digidestined.
Attacks: Trump Sword and Clown Trick
What happened to him: MagnaAngemon used Gate of Destiny, and hasn't been seen since.
Apocolymon (Not a Dark Master)
What he did: Tried to destroy both worlds, and the Digidestined.
Attacks: Total Eniolation
What happened to him: He used his attack but the Digivices contained it and destroyed him.
Thanks to The DigiPort