Badass Decay: Averted. While Tai Lung does become kinder, gentler, friendlier, and an all-around good guy and hero, trading his villainous tendencies for snark, he remains as awesome and incredible a fighter as ever—not to mention hes still quite able to unleash his rage and temper on the true Complete Monsters.
Chao is a sadistic dark chi user. In the past, he slaughtered an entire class of young kung fu students at the Jade Palace and killed his former friends, with only Oogway surviving. Upon being freed in the present, he painfully possesses Vachir-leaving his soul in helpless residence—and murders at least 50 people, including children, and displays their corpses to get Tai Lung to face him. He corrupts the Sacred Pool to control everyone in the Valley, creating a Kangaroo Court and a mob to hunt down Tai Lung when he's put on trial for a murder he's been framed for. He forces Monkey to seemingly kill Mantis, causing him overwhelming guilt. To enrich his dark chi, Chao hangs a couple on grappling hooks to bleed out while their son's gutted body is between them. While he was imprisoned, his soul helped drive Tai Lung into committing his rampage, as well as keeping him focused on revenge and claiming the Dragon Scroll while the snow leopard was held in Chorh-Gom. Betraying Xiu in the end despite her unwavering loyalty, Chao was a sadist who wanted to live forever and force his vision of perfection on the world.
The aforementioned Xiu is Chao's death-loving Psycho Supporter who desires to be the best assassin in her empire. She killed her own father for being "weak" and framed it on her sister, Jia, making her a wanted criminal. Xiu twisted and manipulated Jia into serving her as an assassin who believed her father's death was her fault. She poisoned countless soldiers who had been fighting the Huns and caused others to abandon or betray China just to avoid that fate. Upon being discovered as a traitor, she murdered her kung fu master and fled. She tried to manipulate Tai Lung into joining her with lies about his family, including planting doubts regarding Shifu and Oogway's love and pride in him. She kidnaps and traumatizes Ping, kills Zhuang and frames Tai Lung for it, and makes multiple attempts to kill Po and Tigress. She is willing to let her sisters die to achieve her goals, and after they start having second thoughts and try to resist her, she is determined to kill them when she no longer needs them anymore.
Foe Romance Subtext: Heian Chao is just a little too obsessed with Tai Lung and making him his own, whether the snow leopard wants it or not Apparently it's noticeable enough for even Emotionless Girl Chun to remark on it: "Don't worry, we'll keep [Jia] well away from him. Wouldn't want to interfere with your own plans to have the stud all to yourself."
Chao is the perfect antagonist for Tai Lung. Why? Through corrupting and manipulating his chi, he intends to take Tai Lungs self away. Not only is that at the heart of kung fu philosophy, its the problem Tai Lung had all along, not believing in himself so that he felt he would be nothing without the Dragon Scroll. Ergo, take away his self, and hed immediately be back to the monster he was before.
Thanks to the species of the characters involved, any time Tigress is facing one of the Wu Sisters it's a literal Cat Fight. However, every single one of those encounters is taken absolutely serious and is a deadly, legitimate battle rather than fanservice or amusing bickering (although a bit of the latter does precede the Tigress/Xiu combat in the birch forest). The same also holds true for Mei Ling vs. Jia during the Final Battle, and her earlier fight with all three of the Wu Sisters. Objectification of women defied!
According to Word of God, an appropriate voice for Hai the elephant would be Dianne Wiest. This is the woman who, as the Evil Queen of The 10th Kingdom, spoke the line, "If I hear one whisper, one rumor, that anything is amiss, I will kill your children in front of you." This is precisely what happened to poor Hai herself.
The death of Vachir, already a poignant, powerful, Tear Jerker-laden scene, became this after the death of Michael Clarke Duncan. The whole scene prior to this in fact does a splendid job of honoring the nobility, gravitas, and acting ability of the character's VA.
When Tai Lung is attempting to 'lighten the mood' on the way to Chorh-Gom by helping Tigress and Shifu reconcile, Tigress has this to say: "And since when have you become an expert on entertainment and leisure? Did you take up clowning when I wasn't looking?" No...but as she'll discover, Ping has◊. (And now that that image is in your head, just try and keep from imagining Tai Lung doing and saying all the things the goose did when Tigress was sick.)
In Chapter 38, Tai Lung's thoughts: "No one needed to know he'd been so caught up in romancing Tigress he might not have noticed if Po had started dressing up in a cheongsam. Oh gods...why did I have to go there? Someone kill me now, please...or at least murder my imagination." Well it may not be a cheongsam, but we have gotten to see Po dressed as a woman in "Ladies of the Shade". And Tai Lung's reaction is pretty apt.
On a related note, Song herself being a violet-eyed snow leopardess who is nominally on the side of the bad guys, performs a HeelFace Turn to help fight her former allies, and has a Ship Tease with Po sounds a lot like Jia.
The Big Bad is a dark master of chi who used to be allied with Master Oogway, but was eventually corrupted by his lust for power, leading Oogway to seal him away until he finally made his return centuries later, after Oogway's death. Sounds an awful lot like Kai, doesn't it?
The third movie also has a moment where a panda dons Master Flying Rhino's armor (and which Po himself admitted to fantasizing about), and the statues of the Vault of Heroes appearing uncovered and open on the mountain around the stairs... And considering both Heian Chao and Kai are spirits, it's surely the case that Chao was also immune to the Wuxi Finger Hold, which makes Tai Lung warning Po not to use it incredibly prescient. It's a good thing the possibilities he suggested never happened with Kai, isn't it?
Tai Lung: Just what d'you suppose would happen if you used the ultimate chi move on the ultimate master of chi? The least that would happen is it blowing up in your face and doing absolutely nothing. Worse, you might just make him stronger...or allow him to turn it back on you, corrupt you, vaporize you...
Another more minor point of amusement: in the author's about me page, he notes that the voice he had in mind for Bao (Po's father in this fanfiction) was Bryan Cranston. Out comes Kung Fu Panda 3, and guess who Po's canon father is voiced by?
Ho Yay: Very much unintentional, but some might see this for Mantis/Monkey and Zhuang/Tai Lung, as well as Tai Lung and Po.
Les Yay: There seems to be a bit of this between Chun and Tigress in the final fight.
Like You Would Really Do It: Somewhat subverted, for while neither Tai Lung nor Po die, a number of instances occur where it looks like they have or will, and such was the skill of the writing that none of the readers seemed to believe the author wouldnt have the guts to kill them off. This may have been helped by other matters such as the Disney Death of Mantis and the actual deaths of Zhuang and Vachir.
Magnificent Bitch: Xiu, in the extreme—since as noted above, what is probably her worst act would be killing her own father while framing Jia for it, yet also managing to make Jia believe she was to blame so that she would obediently stay under her thumb as an assassin for fifteen years.
Moe: Nearly every child in the story, including Tai Lung, but Yi especially stands out.
Moral Event Horizon: Though no one was planning to nominate either of them for sainthood, Xius murder of Zhuang and Chao first killing children and then his fellow masters both made them utterly irredeemable and had readers crying out for their blood.
Romantic Plot Tumor: Averted. Though Tai Lung and Tigresss romance is important, particularly to his development as a character and his ability to resist the Big Bad, and quite a bit of time is devoted to it, it was always planned to be so. At the same time, theres much much more going on in the story than just this, as the length of the main page can attest.
Strawman Has a Point: Most of the naysayers, from Tigress to the various villagers, have rather good points regarding the possibility of accepting Tai Lung back into the Valley, either based on him truly having done reprehensible things which need to be acknowledged and punished or by raising very legitimate fears that such a thing could happen again if he did not learn to control his temper or wasn't truly attempting to redeem himself. While Chang and Xiulan fill such roles, Vachir in particular has a number of points since not only did he lose family members as the others did, he was actually the legitimate authority in charge of imprisoning and punishing the snow leopard. Even the fact that Chang was a misogynist, Xiulan a rather self-righteous and narrow-minded shrew of a wife, and Vachir was revealed to be a torturous bully (and that the latter two both got possessed and manipulated into truly heinous acts by Chao) did not change the ultimate sensibility of some of their points—something which Tai Lung himself acknowledged as he struggled to change, prove himself, and remain true to his new path. Deliberate and intentional by Word of God as part of the fic's Gray and Grey Morality.
A number of them, but mainly Zhuang's death and subsequent funeral.
Vachir's final moment, one of the most powerful moments in the fic!
Any scene where Monkey is feeling guilty for killing Mantis.
What Could Have Been: A number of original ideas for the first movie which were either later reworked for the TV series and sequels or which never appeared in canon are employed by the author in just as varied of manners.
The Bandit Inn appears as the mercenary den where Chao hires the Wu Sisters.
Tai Lung's connection with the Wu Sisters is revisited, only instead of them being part of his army they are someone he met before his rampage (and who helped push him into it by playing off his insecurities and belief he would never be truly accepted or loved by Shifu).
The lily-covered lake that was an initial concept for where Tai Lung would fight the Five is repurposed as the locale where he and Po fight the Wu Sisters.
The kung fu training ground where Tai Lung met with his army becomes the place where the Wu Sisters make their base (and meet with Chao).
A creepy image of the Wu Sisters in a moonlit birch forest shows up when they have their fight with Tigress.
Early concept art of Tai Lung, looking far smaller and more lithe (as well as a lighter beige color) is used for Wu Xuan, the father of Mei Ling and the Wu Sisters.
An image of Tai Lung chained in a simple prison cell, before all the levels and barriers for Chorh-Gom were invented, is recreated when he has been arrested for the murder of Shen Zhuang.
The outfits worn by the Five to either the Ghost Festival, Emperor Chen's visit, or both are all references to their original character designs, while Shifu's golden robes are those worn by a "Golden Bear" who was an early Po concept.
The Vault of Heroes, an underground cavern shrine to ancient kung fu masters filled with giant 100-foot statuary and housed beneath the Jade Palace steps, was originally going to be the site of Po's Final Battle with Tai Lung, complete with statues of a snow leopard and panda. Here it is where Chao was imprisoned, and where the Final Battle between his forces and the Jade Palace crew takes place. (Another form of it appeared as the statues surrounding the stairs to the Jade Palace in Kung Fu Panda 3.)