General Kai

Kai fought alongside Oogway as best friends, but after he learned how to steal the chi of others, Oogway banished him to the Spirit Realm. Across five hundred years, Kai stole the chi off of every kung fu master that entered the Spirit Realm, turning them into Jombies. Once stealing Oogway's chi, Kai returned to the mortal realm as a Spirit Warrior and sought to steal the chi from all living kung fu masters and destroy Oogway's legacy. With the help of his jombies, he nearly accomplished his goal, but he was eventually defeated by Po.

During his time as a mortal, Kai was fiercely devoted to fighting alongside and protecting Oogway, whom he loved like a brother. Kai was willing to risk his own life in order to keep Oogway safe; after the tortoise was injured in an ambush, Kai carried him for days across hostile terrain in a desperate attempt to find help. However, their relationship was broken beyond repair after stumbling upon the panda village and discovering the power of chi. Unlike Oogway, Kai became interested in stealing the chi of others in order to increase his own power, learning how it could be taken as easily as it was given. Because Oogway prevented him from fulfilling his ambition and imprisoned him for centuries in the Spirit Realm, he felt Oogway betrayed him and had never, or would ever, recover from the pain of losing the only person he ever truly loved.

After his banishment, Kai's anger and hatred grew ever stronger against Oogway, demanding a rematch, which ended with Kai stealing Oogway's chi and returning to the mortal realm, but as a Spirit Warrior, to exact total vengeance against Oogway by destroying his legacy. Kai's disposition was worsened, if anything, during his time in the Spirit Realm as his sense of humor was darkened, and where there was once loyalty and honor, cruelty and aggression had replaced; however, he could still be amused by certain things, as when attacking Po at the panda village, and two pandas used a technique called the "belly gong" against one of his warriors, Kai simply did a double-take and muttered to himself "seriously?" with an amused smile on his face. To further his lack of morals, Kai was blinded by his own repute and was devoted heavily to his legacy, displeased that none recalled or even had heard of Kai, the "Beast of Vengeance" or "Maker of Widows" and so had no qualms whatsoever about destroying Oogway's legacy, believing that he had destroyed his. However, Kai was quite pleased when Po addressed him with said titles, even thanking him quite politely and claiming that it made him almost want to spare his life. Of course, that did not stop Kai from trying to steal Po's chi along with the rest of the pandas. Kai was also often annoyed by Po's sense of humor and underestimated him, just like nearly all of Po's previous adversaries, but he was ultimately defeated by Po who overloaded him with chi, leading to his demise. He can also be very chatty as Po annoys him with the chit chat.

After being defeated by Po, Kai seems to have learned what Oogway warned him. After being overloaded by the Dragon Warrior's chi, Kai seems to have completely abandoned the idea of stealing the chi of other masters (and presumably lost the ability to do so) and accepted to live in peace in the world of the spirits. When he was summoned by the Chameleon, he showed no interest in attacking Po when he was freed, made peace with him and returned happily to the Spirit World.

Kai is a large, muscular light gray supernatural yak with glowing green eyes, long black hair, a helmet, two enormous horns that are shaped like flames and they're very thick, a green pendant of collected chi, a brown loincloth made of layered leather, and muscular arms with brown bracers.