Etemon is the Master of the Dark Network, and it's power lets him prevent his enemies from Digivolving. This Elvis impersonator became even more dangerous when he absorbed Seraphimon's fractal codes and Digivolved to KingEtemon. His ultimate goal is to recreate the ancient enemy Apocalymon.
Kuwagamon was the first enemy in the anime, also, but the Digibusters soon had far worse to deal with far worse...
Ogremon was Leomon's rival, and is KingEtemon's right-hand man
These three prehistoric thugs are KingEtemon's "band"
Flamon and Strabimon were a couple of thugs in the service of TyrantKabuterimon; SnowAgumon and Biyomon were would-be train robbers. All have in common the fact that they somehow found or were given four of the five Beast Spirits that will give the Digibusters greater power.
Tankdramon leads a unit of the D-Brigade, a mercenary army currently in the employ of TyrantKabuterimon. The Commandramon under him have names: their leader is Sgt. Gingrich, and others are Stoner, Buchanan, O'Reilly, and Gramm.