Gate

Gate is one scientist that found a piece of Zero in the remains of space colony Eluria, destroyed in Mega Man X5. He was able to understand part of it, but he turned into one Maverick and created the Nightmare Phenomenon and High Max. He also ressurected Sigma. Before turning into a Maverick, he was a scientist friend of Alia that created many strong Reploids, but as he frequently desobeys his superiors, he was fired. Gate and some of his most strong creations appears in Mega Man X6. When encountered in the lab, he is a difficult opponent; he can only be damaged by striking his shots and sending the debris back at him--but this is difficult to do without taking damage as well. Also, there is a large pit at the bottom of the room; the only solid ground consists of small platforms. X in Ultimate Armor can try to Nova Strike away to make the shots' debris go back. Zero (preferably in Zero Armor) can use the Rakukojin to hit the shots. But in either case, when his health is low enough, Gate will do a slashing attack that can not only do damage, but the resulting energy wave will temporarily destroy one of the small platforms.