Even though some of the events of Irregular Hunter X do not match with Mega Man X1's, and the comic follows the MMX1-MMX8 official timeline, this statement along with many others are still being considered as valid in the universe of Mega Man X: Unit 49.
Unlimited Evolutionary Potential is the term used to describe the meaning of X's name: a variable which can stand for any number and thus unlimited capabilities, as Dr. Thomas Light said in X's flashback, in The Day of Σ.
An unknown mechanism in X's body allows him to change and adapt himself to be physically stronger as time goes by, granting him new powers after certain situations. (Not to be confused with the Variable Weapon System.). X can even use traces left by data of armors and rarely weapons, that were left somewhere in his body. The most notable examples are the Dash Program, adapted from the Light Armor in the beginning of the Maverick Wars and, only after a decade, the Air Dash, developed an uncertain time after Mega Man X6.
In desperate situations, X have a chance of unleashing a power unknown even by Dr.Cain: his crystal glows and his hands are charged with an indefinite amount of energy, coming from an unknown source.
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This content section may contain spoilers about the plot of the comic.
The conditions to activate this Unlimited Mode remain undefined, since X experienced many breathtaking situations and nothing happened.
In the first occasion this mode has been activated, X was practically defeated by Sigma, a stronger enemy with an undying will. X has shown to be as much as determined than his enemy and the power has been unleashed briefly before he deactivated due to severe damage.
In his fight against Kran in Shattered Shine, Kran proved to be strong enough to defeat X and even forced him to give up on trying to solve things peacefully with him, then managed to catch X in his finishing move. X would cease efforts to resist in a few moments when his will was refilled and the Unlimited Mode unleashed, due to him realizing that power by itself would not be of any use if you can't use it to open your own eyes to a world of peace and he needed to win this fight at any cost.
- Speculation 1: The way both cases unfolded could point out that one of the factors that lead to the activation of the Unlimited Mode is the understanding of why X should keep fighting stronger and more willed opponents, no matter what happens, because his objective is far above theirs. At the moment of this insight, a phenomenon happens as if the parts responsible for his Unlimited Evolutionary Potential were awakened for a brief moment and his body started to adapt itself to become as stronger as it's needed to win the fight.
- Speculation 2: The glowing hands effect happens when his Energy Amplification Device is briefly adapted to produce an indefinite amount of energy. The reason X cannot consciously activate this setting is that Dr. Light feared a potential like this could be dangerous and a disaster could happen if X couldn't control it.