Tai Lung

"He's a panda! You're a panda! What are you going to do, big guy? Sit on me? *chuckles*"

- Tai Lung confronting Po for the first time

Tai Lung is the main antagonist of Kung Fu Panda. He was Po's nemesis, Shifu's former student and adoptive son, and Tigress' adoptive older brother.

Beginnings
Tai Lung was found as a cub by Master Shifu. Shifu raised him as his own son, having "loved him like no other", and trained him in the arts of Kung Fu.

Tai Lung became a formidable fighter, and was the first to master the thousand scrolls of Kung Fu. But even that power wasn't enough for him. He wanted the Dragon Scroll, which was believed to hold the secret to limitless power, to which it acted as the source of Tai Lung's growing pride.

But Shifu's mentor Grand Master Oogway sensed his overwhelming pride that would result unpleasant pursuits, and respectfully refused to let him have it. At that rate, Tai Lung's pride turned into rage, and Tai Lung took it out by laying waste to the Valley of Peace, and tried to take the scroll by force, where Master Oogway and Master Shifu were waiting for him.

Shifu attempted to stop Tai Lung on his rampage, but was unwilling to harm the one who he considered to be a son. Tai Lung did not hesitate to push Shifu out of the way, crippling him in the process, due to the fact that Shifu was unable to stand up for Tai Lung when Oogway denied him the Dragon Scroll. Just before Tai Lung was about to get hold of the Dragon Scroll, he was stopped by Master Oogway, who blocked up his chi, rendering him unconscious.

He was then locked into a prison with thousands of guards, weapons, two boulders chained to his arms, and a jade shell on his back to immobilize him as punishment for his crimes against the Valley.

In Kung Fu Panda
20 years later, Tai Lung escapes from Chorh-Gom Prison; meanwhile, in the Valley of Peace, the potential Dragon Warrior (Po) is being trained to fight Tai Lung. But the problem is that while Tai Lung was locked away, he had much time to meditate, and became stronger than ever before. He is faster, stronger, and now more powerful than his former father and teacher Master Shifu.

During the final battle, he and Po came face-to-face and fought over the Dragon Scroll themselves and tried to outdo each other and retrieve the scroll (that was before Tai Lung could kill Shifu with his claws for the scroll when he found out it was gone and Po took it).

After the fight, Po managed to defeat (and supposedly kill) Tai Lung by using the Wuxi Finger Hold, which causes a huge gold explosion that ends his reign of terror.

Trivia

 * Tai Lung appeared in the first Kung Fu Panda video game, in which he was the primary villain again and, just like the movie, broke out of jail and went for the scroll; however, unlike the movie, the Furious Five get captured by the leopard and his army of wolves. So it is up to Po to go rescue them and stop Tai Lung.
 * He returns in the video game Kung Fu Panda: Legendary Warriors, in which he's the main villain (again) and also the final boss. This time, he comes with a troop of enemies to aid him. He's once again stopped, defeated, and killed by Po and the others.
 * According to the creator's commentary, Tai Lung saw himself as the hero of the movie, hence his golden eyes.