Naruto's most powerful monster is the Ten-Tailed beast, a demon with a tragic origin that began with the noblest of intentions, but soured into evil!

Across the Naruto mythos, with all the ninja clans, backstabbing villains, and horrendous monsters, there is one that is the most powerful, the Ten-Tailed beast. Being born of jealousy and envious of godly power, Ten-Tails’ story of how it attained the level of power it now possesses is one of heartbreak and sorrow, though entirely self-inflicted. Originating at the dawn of human-accessible chakra, Ten-Tails is an elder demon that was once a human that became a twisted form of her former self in the path to attain ultimate power.

Ten-Tails was originally a princess in an ancient past riddled with war. There was a tree that was revered as a god known as the God Tree, one which offered a chakra fruit every thousand years. With the fruit, humans could do things they otherwise couldn’t even dream of, similar to Naruto's present-day abilities. Wanting to make chakra a lasting advantage to her people, Princess Kaguya planted the seeds of the fruit, creating sustainable access to chakra. Not long after, she became pregnant with two sons, who were the first to be born with chakra, not needing any outside help to attain the powers it offers. Jealousy grew within the princess, believing that her children stole the chakra that rightfully was hers, so she did something drastic.

Kayuga later combined with the God Tree in her quest for power, becoming the first incarnation of the Ten-Tailed beast. Kayuga ravaged the land she once made strides to protect, all the while battling her own sons for a power she believed was stolen from her. Eventually, Ten-Tails was imprisoned in the moon where she remained for some time. While the story of her origin is tragic, it is clear that Kayuga was corrupted by her own lust for power and became a demon while choosing strength over her sons, and that corruption was made clear by being one of the most horrific looking creatures in Naruto.

While Ten-Tails has the ability to change its appearance, none of the options for how it can look are good. Some features remain, with the most prominent being a single eye that takes up most of its head and spiky protrusions growing out of its back. The most beastly of forms is Ten-Tails' titan-like form with a large mouth and razor teeth, the largest and one of the most physically intimidating. Another form straight out of a horror manga is the shape of an emaciated humanoid with elongated limbs and a twisting neck. While the many versions of Ten-Tails are incredibly scary, the beast can back up the induced fear with the raw power it possesses.

First appearing in Naruto Vol. 50 Chapter 467 by Masashi Kishimoto, Ten-Tails wasted no time demonstrating why it is the most powerful monster Naruto has ever faced. A dark cult-like group is trying to resurrect Ten-Tails in its original body, and the prospect of that happening would mean the assured end of the world. Fear-inducing forms and world-ending power to back it up, introduced in its very first appearance, wasting no time to establish the monster as a serious threat proves the Ten-Tailed beast is Naruto’s most powerful monster!