Kai the Collector

"You must be the Dragon Warrior?"

- Kai going face to face with Po. "KAI HAS RETURNED!!"

- Kai gloats about his return to the mortal world.

Kai, also known as The Collector, is the main antagonist of Dreamworks' 2016 animated movie Kung Fu Panda 3. He was the former brother-in-arms of Oogway and, upon his return to the mortal realm, he became a Spirit Warrior; and thus that he can steal kung fu warriors' chi from them and his scheme is to defeat every kung fu master and also Po, the Dragon Warrior, the one who will defeat him in order to take over China.

He is voiced by J.K. Simmons, who also portrayed Terence Fletcher and J. Jonah Jameson.

Description
According to a summary of the film, Po is to face The Collector, an "evil spirit" who can steal the kung fu powers from others. As he begins defeating kung fu masters across China, Po will attempt to stop him with the aid of his fellow pandas.

Appearance
Kai has the appearance of an anthropomorphic yak with green glowing eyes, long black hair, a helmet, two enormous horns shaped like flames and very thick, muscular arms with bracers.

Early Years
Many years ago, Kai and Oogway fought together as brothers-in-arms, and were close friends. During a fight, Oogway was badly injured, and Kai carried him for days, searching for help, until they happened upon a secret panda village, where the pandas used their knowledge of chi to heal Oogway. Fascinated by the power, Oogway was taught by the pandas on how to utilize it. Kai, however, became interested solely in using the chi of others to increase his own power. The two former allies fought, and Oogway triumphed, banishing Kai to the spirit realm, where he was imprisoned for the last 500 years.

Returning to the Mortal Realm and Po's Reveal About Him
In the spirit realm, Kai challenged Oogway to a rematch, and though the two were equal in skill and power, Oogway willingly gave in and allowed his chi to be taken, but not before telling Kai that he had set another on the path that would defeat him. Kai vows to defeat this warrior and uses Oogway's chi to return to the mortal world. After re-emerging back in the mortal world, Kai sent out several of his jades minions to scout for him and find Oogway's students. The jade statues attack the Valley of Peace and fight against Po, Shifu and the Furious Five. Po notices that some of the jade statues resemble past Kung Fu masters before they retreat. The team then learn through research that Kai was Oogway's old friend who fought with him as brothers long ago. When Oogway was injured, Kai carried him until they reached a secret village of pandas, who healed Oogway using their chi. While Oogway learned the way of the chi, Kai was jealous and wanted the same power and ended up betraying Oogway, but was defeated and banished to the spirit realm for 500 years. In order to defeat Kai, Po must learn to channel chi himself, which Li offers to teach him in exchange for going to the secret panda village where Li came from.

Attacking the Furious Five and Shifu
After learning that many Kung Fu masters are missing by Kai, Shifu sends Crane and Mantis to find Kai but avoid engaging him. Crane and Mantis join with Master Bear, Master Croc and Master Chicken to confront Kai, but one by one they are all easily defeated and have their chi stolen. Kai then arrives at the Jade Palace and destroys it, but not before stealing the chi of Monkey, Viper and Shifu. Tigress escapes to find Po and warns him about Kai.

The Final Battle with Po and Death
Kai arrives and confronts Po, who had been waiting for him. Kai sends his minions to capture Po, but they are held off by the pandas, distracting Kai. The plan works at first, but ultimately fails when Po tries to use the Wuxi finger hold on Kai, who reveals that it can only work on mortals, which he is not. Kai gains the upper hand in their fight, but Po grabs Oogway's chi around Kai's neck and uses the Wuxi finger hold again, this time sending them both to the spirit realm. They fight again, but Kai defeats Po and prepares to take away his chi. Using what they learned from Po and about who they are, Li, Tigress, Mr. Ping and the pandas are able to use their chi to save him. Po becomes a true master of chi and infuses his chi into Kai's body. Though it would seem Kai has finally achieved his goal to take Po's chi, he learns too late that Po's collective chi is too powerful for him to control, much to his dismay. With that in mind, Kai can only scream in defeat as Po's chi finally overwhelms his body and the evil yak disintegrates into a bright light, ending his terror for good. Kai's death also allowed all the kung fu masters' chi to return back to the mortal world, much to their delight.

Personality
Long ago, the fearsome and power-hungry warrior Kai found a way to take chi from others, until he was banished to the Spirit Realm for all eternity. Now, Kai has returned to Earth, where his appetite for power and revenge leads to an incredible showdown and battle with Po. There is currently little known about Kai's personality, though he is described as being an "evil spirit." .

Kai's voice actor, J.K. Simmons, has said that Kai will be "not happy about life in general," but will have a sense of humor, "even if it is a little bit dark." He added that Kai is also vengeful, and a "bitter, bitter guy."

Kai holds great hatred for his former friend, Oogway, stating that he "loved him like a brother", and believes that Oogway betrayed him. It is possible that he holds the Pandas responsible for turning Oogway against him from teaching him the ways of chi.

Fighting style and abilities
Kai fights primarily with a set of jade swords attached to long chains. He has also been seen wielding axe-like blades, indicating that he is skillful with multiple weapons. Kai is described as a "supernatural villain" ,which indicates that he possesses supernatural powers. It was later revealed that Kai possesses the ability to "steal the powers from every kung fu master he defeats,"particularly their chi.undefinedAfter absorbing the chi of someone, the victim in question is transformed into a small, jade ornament that Kai wears on his belt, and when needed, he can summon these figures, turning them into jade, statue-like creatures, and see through their eyes. Since he is a "Spirit Warrior", he cannot die by natural means nor by most Kung Fu Techniques, because he is not alive, in essence at least. However, this does not mean he cannot be destroyed. He also has an advanced amount of supernatural strength, speed, stamina & durability.

Quotes
"With your chi, I will finally be able to return to the mortal world, and this time.... you won't be there to stop me."

- Kai after seemingly defeating Oogway in the battle in the spirit world "Kai has RETURNED!!"

- Kai gloating about his return to the mortal world "You must be the Dragon Warrior? (Po: And you must be Kai.... Beast of Vengeance, Maker of Widows!) YES!! FINALLY!! Thank you! Almost makes me wanna spare your life!"

- Kai after meeting with Po for the first time and complimenting him for knowing his aliases "Round them all up."

- Kai summoning the captured souls of the kung fu masters to eliminate Po and the pandas. "Oh no! It's working! No, no! (gags, but later chuckles) No, it's not. Did Oogway teach you that little trick? Too bad, it only works on mortals, and I.... am a spirit warrior."

- Kai mocking Po when the latter tried to use the Wuxi Finger Hold on him "So, Oogway, this was the one destined to stop me? I will have his chi, and then all of them! (to Po) And you.... (chuckles) ..... you really thought you could send me back to the spirit realm? (chuckles) You are just a stupid mortal."

- Kai gloating to Po and the pandas.

"It took me 500 years too take Oogway's chi. I will have yours if it takes me 500 MORE!"

- Kai to Po before attempting to finish the final blow.

"YES!!! The power.... is MINE!! Wait a minute! No! It's too much! It's TOO MUCH!! NO! UGH!!! NOOOOOOOOO!!!!!!"

- Kai's last words as Po's powerful chi overwhelmed him

Trivia

 * Kai share at least two similitudes with Tai Lung and Lord Shen, the main antagonists of the first two Kung Fu Panda movies: they are all vengeful and evil from the past and don't see Po as a threat until the end of the film which make them mocking and underestimating Po, which led to their final deaths.
 * In Chinese, the name Kai most often translates to "victory" (traditional Chinese: 凱 simplified Chinese: 凯; pinyin: kǎi) or "open" (traditional Chinese: 開; simplified Chinese: 开; pinyin: kāi).
 * Kai was previously reported to be voiced by Mads Mikkelsen. However, he dropped from the film due to unknown scheduling issues.
 * His design is similar to Drago Bludvist from the 2014 DreamWorks film How to Train Your Dragon 2.
 * He is one of the few demonic villains who appeared in Kung Fu Panda franchise, alongside Ke-Pa and his demon army, Jiang Shi and the Mongolian Fist Demon.
 * Kai uses swords on chains like Kratos - anti-hero from God of War.
 * Kai is similar with Tirek from My Little Pony Friendship Is Magic: they both steal power from enemies they encounter (Tirek stealing magic from ponies around the world of Equestria and along with Discord's chaos magic to try to be ever powerful and to rule Equestria. And Kai defeats many Kung Fu masters and steals their chi and to use them to attack more Kung Fu masters across China to steal more chi to try to destroy Po and all other pandas and to rule all of China.)
 * His is death is similar to Octomous the Master's death from Power Rangers Mystic Force as they both tried to devour a certain type of power (magic, Octomous, Chi, Kai) but they eventually got destroyed because they could not have any more.