Makaio-Ken

Makaio-Ken(魔界王拳, Lit. "Fist of The Underworld King") is the modified and superior version of Kaio-ken that was invented and used by The Grand Supreme Dark Kai. It is many times superior to its original counterpart, granting greater power to the user and outpacing the Kaio-ken in all aspects by a heavy amount. However, it is an extremely forbidden technique due to the extreme risk of life that it puts on the users body, being far more deadly and dangerous than that of its original, kai counterpart.

Description
Makaio-Ken, developed from Kaio-Ken, is the greatly superior and more powerful technique, invented by The Grand Supreme Makaioshin. It is triggered in the same fashion as its original variant, by shouting "Makaio-Ken" once multiplies their ki for a heartbeat. However, instead of a measly 2, The Makaio-Ken increases the users Ki by a massive leap of 10 times their normal energy output. This is why it is a forbidden technique even among the members of Mu's 12 Demon God Fists. Not only that, but the user has no control over the multiplications or when they occur, and the technique cannot be disengaged at just any moment the user wills it. Instead, the multiplications come faster and become more frequent, putting more and more strain on the users body and potentially destroying them altogether in the end. The speed of the 10X increase can reach as fast as nanoseconds, picoseconds etc etc, accelerating in speed indefinitely. Mu himself is the only one that has shown the ability to use this technique with no negative drawbacks.