Shen vs. Kai: When Evil Collides is a What If? fic for Kung Fu Panda created by Berserker88 and later co-authored with Mind Jack. Taking place during the events of Kung Fu Panda 2, the fic follows the events of canon, with Big Bad Lord Shen creating an unstoppable new weapon, invading Gongmen City, and plotting the conquest of all of China. The heroes of the Jade Palace set out to stop him, as per usual.
And that's where Kai comes in.
The tides of fate have suddenly gone out of whack and the Maker of Widows has broken out of the Spirit Realm much earlier than he should have, now leaving the heroes with two villains to contend with. Luckily for them, the baddies are more interested in removing their competition so they can have China all to themselves. This quickly results in one hell of a chaotic situation and multiple levels of Mind Screw.
Shen vs. Kai: When Evil Collides provides examples of:
- Accidental Misnaming: Kai named his second strongest Jade warrior Taiwan. When Mantis tries to correct him, Kai interrupts him in favor of gushing about Tai Lung's abilities.
- Ascended Extra: Two unseen Jade warriors; Oogway and Tai Lung make an appearance in this fic as Kai's two strongest warriors with Kai expressing great displeasure at the fact that he is forced to use the former.
- Bat Out of Hell: Played quite literally with Hei Yinying.
- Big Bad: Kai, with Shen as more of a Villain Protagonist. Or so it seems. Kai himself is just an Unwitting Pawn to Hei Yinying.
- Bilingual Bonus: Hei Yinying - Mandarin for Dark Cloudy Shadow.
- Black Comedy:
- As a fic heavily involving Kai, this is a given.
- Yinying engages in a bit of this as well. Not surprising, being a death demon and all.
- Casting a Shadow: Yinying's main abilities.
- Deal with the Devil: As it turns out, the entire fic is the result of one, made by Lord Shen as a means of getting a second chance at life. Needless to say, it isn't as simple as that.
- Drama-Preserving Handicap: When Kai summons him, Jade Oogway proves to be the strongest jombie in his arsenal, as he is able to repel every single wolf swarming him and could have flattened any opposition, including the Furious Five and Shen, but since summoning him hits one of Kai's Berserk Buttons (being reminded just how inferior he is to Oogway), he never uses him unless he has no other choice.
- Even Evil Has Standards: After the Soothsayer manages to convince Kai to leave his own base by constantly pestering him with questions, Kai ultimately decides to take his frustration out on some old buildings, as even he can't find it in him to beat up an old lady.
- Evil vs. Evil: The central premise.
- Glowing Eyes of Doom: Comes with Kai's Jombies.
- Godzilla Threshold: Using Oogway is this to Kai; He is easily the strongest Jade Warrior that Kai has in his arsenal, but due to being a big Berserk Button for him, he never uses him unless he absolutely has to. Which unfortunately, Boss Wolf managed to force him to and makes Kai incredibly angry.
- Hidden Villain: Yinying, who (literally) stays in the shadows for most of the fic.
- Hope Spot: A particularly brutal one. In Chapter 20, Po defeats Yinying in a battle for Shen's soul contract, which the demon is forced to hand over to him. Po is about to destroy it and release Shen from his deal, when Yinying casually mentions that it was this contract that created the Alternate Universe the fic takes place in, and destroying it will essentially cause said universe and everyone in it except Shen to cease to exist. Yinying then explains that he knew this the entire time and only went through all of this trouble solely to break Po's spirit. And it works.
- Hypocritical Humor: When Kai first hears his jade soldiers referred to as "jombies", he calls the name ridiculous. By the next chapter, he's using it himself.
- Laser-Guided Karma: Lord Shen, by the end of the story, is punished for his crime of attempted panda genocide by being reborn as a panda.
- Off the Rails: The fic follows the plot of the second film to a tee up until Kai gets involved, throwing the entire thing off track almost immediately.
- Out of Focus: The actual heroes, spending most of the first act just trying to get to Gongmen after Kai inadvertently destroys their boat. They get more prominent once they finally arrive.
- Please Select New City Name: Discussed Trope. Kai considered renaming Gongmen City into either 'Great Kai City', 'Kaiopolis' or 'Shi Kai De' during his confrontation with Monkey and Viper.
- Take My Hand : Monkey and Viper have such a moment when trying to escape Kai. Neither of them makes it, and Kai only refrained from grabbing them immediately because he was curious to see what would happen.
- Traveling at the Speed of Plot: On their way to Gongmen City, Po and the Five are inadvertently delayed by Kai, keeping them from interfering in the initial struggle between the two villains. They only reach the city just in time to find the injured Shen.
- Ungrateful Bastard: Shen doesn't much appreciate being rescued. The Furious Five take the time to tend to his wounds and immediately after, he insults Viper and Monkey while they are out of reach, attempts to take Mantis hostage, and later on, orders his henchmen to apprehend the surviving warriors.
- Unwitting Pawn: It turns out that Kai is merely a pawn to Hei Yinying, a mysterious demon whom he made a deal with to escape the Spirit Realm. The same could be said about Shen, and to an even greater extent.
- Villain Protagonist: Lord Shen takes on this role, with Kai being the more explicit villain.
- Walking Spoiler: Yinying's existence isn't so much as hinted at until Chapter 7. And he doesn't physically appear until Chapter 16.
- You Called Me "X"; It Must Be Serious: Like the original, Shen always called Po by his animal name "Panda", but when he witnessed Po having a Heroic BSoD, he calls Po by his name after his attempts to call him "Panda" proved futile. And it's also what made Po finally respond to him.