Mephistomon

Mephistomon is evil Digimon born from the remains of Apocalymon. Like his 'father', Mephistomon had a deep hatred for all life & plotted to kill every human & destroy the world. To acommplish that, he took on the alias of Ryuuji Tamashiro, the young president of an newlly build Okinawan venture enterprise, VP Laboratories. He became famous for creating the V-Pet, a popular pet software, but serving to bring other Digimon as evil as Mephistomon to the human world.

He eventually revealed himself when he found the location of the Vaccine program that would undo his plans. But he had to deal with the Tamers, dragging them & everyoneelse under the oceans to a post-apocalic dimension modeled after what would result to the real world. After he was deafeated, & the Vaccine ran it's course, Mephistomon digivolved to Gulfmon & was finally killed off.