Ninetails

Ninetails is a boss from Mega Man X: Command Mission. He is the strongest enemy in the game, and is either the leader of the Tails clan, or its single member with the others possibly being clones (see next paragraph). He and his clansmen/clones are imprisoned in the Central Tower Basement. To confront him you have to get the Central Key and face all the other Tails (Onetails, Twotails, Threetails, Fourtails, Fivetails, Sixtails, Seventails and Eighttails). He's pretty hard to defeat, because he can heal himself automatically. His attack "Nine Fragments" refers to his nine tails, which he stabs into his enemies rapidly, causing 8991 points of damage (9*999), what is enough to take everyone out. Furthermore he has the ability to completely drain his enemy's weapon energy with his Puncture Arrows, and the Annihilator Hadoken, a large and devastating energy beam, sweeps over the place and inflicts heavy damage to all of his opponents. Because of his attacks it's not a lie when he says: "My strength is unparalleled!"

The game is not clear on whether the other Tails members are "real" reploids or merely lesser-tailed shadow clones of him. Evidence to the latter theory includes the following:
 * Some of the Tails apparently possess the ability to indefinitely clone themselves.
 * Most of the other Tails are basically stronger versions of past enemies. The only attacks indicating otherwise would be Puncture Arrows and the Annihilator Hadoken attack: Ninetails can do both, however, and the latter attack was taken from the fellow Capcom-produced Street Fighter video game series.
 * Each of the Tails actually has the same nine tail spaces visible on their back no matter how many tails are actually there. In fact, the amount of tails is the only difference in all of their appearance.
 * Ninetails is the only Tails boss Axl gets a DNA attack from.
 * The Resistance soldier at Shaft 999F who explains why the area where the Tails are found is off limits says that "apparently a savagely strong prisoner is being held below", hinting towards the idea that there was only one.

In either case, he is an immensely powerful reploid imprisoned by the Resistance in a special sealed section of the Tower which requires the Central Key to open, indicating possible allegiance to the Rebellion or some other highly dangerous form of Maverick activity. This is most likely the latter, as he does not mention the Rebellion or have their emblem anywhere on his person. Moreover, he seems to have no grudge with the Hunters, and wishes only to fight them for the challenge of it.

Instead of normal armaments, Ninetails and his clan/clones utilize a form of robotic chi manipulation similar to that of human martial arts that allows them the ability to utilize powerful energy attacks and techniques without the need of an outside power source. Upon encountering X's team, each of the Tails simply challenges them to a fight, with the exception of Ninetails himself, who, as aforementioned, claims with good reason that his strength is unparalleled.

Trivia

 * Ninetails seems to borrow heavily from the same Japanese fox-spirit folk tales as anime and game characters such as the Pokemon creature Ninetales and the Nine-Tailed Demon Fox from Naruto. One could say that Ninetails would be the game makers' brief attempt at a reploid take on the kitsune legend.
 * Moreover, the Nine-Tailed Fox in Naruto ends up being imprisoned within its series' titular character, who ironically (considering the cloning theory here as it relates to Ninetails and his clan) learns the ability to produce shadow clones of himself, which is greatly assisted by the kitsune demon, in spite of that skill being "forbidden" in that series' canon.