Dark Rockman.EXE (anime)

Dark Rockman (ダークロックマン) is the dark counterpart of Rockman.EXE, created after ShadeMan.EXE bit Rockman, infusing him with a Dark Aura. Although saved with a Vaccine Chip, while returning to Netto Hikari from the past, a ball of light absorbs Rockman's Dark Aura and whisks it away.

History
This all begins when a phenomenon known as a "past vision" allowed the Darkloid ShadeMan to come back to life, in his mutilated form, just before LaserMan deleted him at the end of Axess. To ensure that the Darkloids rule the future, he implemented his data into a rocket and bit MegaMan on the neck. MegaMan's data became tainted, and when the right moment came, he fully converted to the dark side of himself.

Fortunately, Lan remembers the vaccine chip that they had used on Dark ProtoMan. With Lan's aid, MegaMan is able to defeat the darkness, and returns to normal long enough to destroy ShadeMan for good, along with his rocket of Darkloid data. As MegaMan made his way back to Lan, a dark energy separated itself from him, and took off in a blinding flash of light. Mysteriously enough, Dr. Regal is heard laughing in the background.

Five episodes later, MegaMan suddenly attacks all his friends, nearly deleting them. Later that day, he also nearly robs a bank. These actions land MegaMan in jail, much to Lan's anguish. As the two find themselves alone together, MegaMan begs Lan to delete him before he can do any more harm. But Lan refuses, until he realizes that the MegaMan in front of him really isn't MegaMan at all.

The sinister Navi reveals himself to be none other than Dark MegaMan. The real MegaMan became trapped deep in the Internet, where he is being attacked by a new horde of Darkloids: LarkMan, BlizzardMan, CloudMan, and CosmoMan, all under the direct orders of Dark MegaMan himself. Later, Dr. Regal sends Dark MegaMan to attack and enter the past tunnel to access Duo's Comet. Dark MegaMan is defeated by MegaMan in combat, but succeeds in escaping and accessing Duo's Comet. However, Slur intervened and ran her sword through his back. In the end, Dark MegaMan sacrificed himself in order to allow MegaMan to escape, and after his escape, Dark Megaman's data remains fused with MegaMan, as MegaMan had forgiven him.