Dark MegaMan.EXE

Dark MegaMan (ダークロックマン), originally known as MegaMan DS (ロックマンDS) in MegaMan Battle Network 4, is a dark version of MegaMan.EXE created from the darkness of Dark Chips.

MegaMan Battle Network 4
During a fight against ShadeMan.EXE, MegaMan is forced to use a Dark Chip to delete the Darkloid and his Dark Soul is born. Throughout the game, MegaMan is forced to resist/or succumb to the temptation of using Dark Chips. Dark MegaMan appears as an apparition created by Duo.EXE, designed to test MegaMan and see if he is strong enough to conquer the darkness in himself. MegaMan fights his dark soul and triumphs. Dark MegaMan then disappears, with Duo commenting that MegaMan only suppressed the darkness instead of destroying it.

Dark MegaMan appears at the end of Black Earth 2, brought out by the Mirror of Truth. When MegaMan defeats it again, he is awarded a pair of programs for the Navi Customizer.

In both cases, Dark MegaMan has everything the player has, including max HP, NaviCust programs and Program Advances used. It also has the advantage of being able to warp around the battlefield instead of being restricted to four directions. However, its attack choices are rather haphazardly chosen, so a player can out-think it.

MegaMan Battle Network 5
MegaMan transforms into Dark MegaMan again when Nebula captures him and fills his body with dark power and places him in charge of the first half of End Area. After he is defeated during the liberation mission, he returns to normal. The battle with Dark Mega can be easy or hard depending of what kind of chips and weapons the player uses, as it can use all the battle chips and P.A. used in the game until that moment. Unlike the previous game, where his HP total was the same as the players, it's preset by version.

Dark MegaMan can also found in Nebula Area 6 as the Chaos Lord if the player takes two minutes or less to defeat all the DS Navis after their initial defeat. However, there is no bonus for redefeating Dark MegaMan.

Rockman EXE Stream
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 had deleted him at the end of Axess. To ensure that the Darkloids would rule the future, he implemented his data onto a rocket, and bit MegaMan right on the neck with his fangs. MegaMan's data became tainted, and when the right moment came, he fully converted to the dark side of himself.

Thankfully for our fellow blue Navi, 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 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 aura seperated itself from him, and took off in a blinding flash of light. Mysteriously enough we heard Dr. Regal's laugh in the background.

About 4 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.

Indeed, the sinister Navi reveals himself to be known other than Dark MegaMan! The REAL MegaMan became trapped deep in the internet, where he is being attacked by a new hoard of Darkloids; SwallowMan, BlizzardMan, CloudMan and CosmoMan, all under the direct orders of Dark MegaMan himself.

Manga
In the MegaMan NT Warrior manga series, Dark MegaMan and LaserMan mysteriously appeared after a defeated Bass colapes after a controntation with Megaman. Dark Megaman has been causing other net forces to confuse him with the real MegaMan, and he even planned to absorb the last of Bass' power. But to do this, he needed enough energy that stemmed from MegaMan's hatred for him. So, to become strong enough to absorb Bass, ne needed to trick the actual MegaMan into detesting him deeply, often by putting loved ones in danger, like his netop, Lan. He eventually does absorb Bass, and he absorbs LaserMan as well, betraying him. But he eventually gets defeated.