Why was Shen evil? it show first he wanted to make weapons with fireworks gunpower because he wanted to rule over China, but how can he become evil because of that and why he wanted to rule over China that had nothing to do with him and not only his own kingdom. Shen would at least get his will to rule over a kindom since he was even a prince and the only heir after his parents to rule over their own kingdom, usually princes and princesses who have and are jealous of their older siblings who are the next to rule over their kingdom and advisers who dislike their job or never get any praise and honor, become powerhungry and will only rule over their own kingdom instead of entire country or the world that have nothing to with them.
Why did Shen want to make an end of kung fu? Shen was even a kung fu master, kung fu had nothing to do with his backstory, his main goal was to conquer China and kung fu could also be useful to conquer China. Shen created a cannon that would put an end of kung fu, but it's not only kung fu it should make an end of if there are anything else that are as powerful or more powerful than kung fu, like chi.
How could the kung fu masters believe cannon could put an end kung fu, not even first that Shen atleast had more than one cannon to put an end of kung fu and conquer China and create multiple cannons quickly that they should rather stop him from doing instead, and how could even Po believe a cannon figurine was Shen's actual cannon when it was too small too put an end of kung fu and conquer China and didn't even laugh because of that?
Why did only Po and the Furious Five go to stop Shen, wasn't there many other kung fu masters than just Po, the Furious Five, Shifu, Storming Ox and Croc who could also go to stop Shen if they needed more help?
Are not kung fu masters smarter, too quick and has high strength to hit the cannons? The kung fu masters seem weaker than they normally are because of they doubted over themselves because of the cannon, but cannon is too slow and heavy to swing fast enough to shoot and can't shoot in all directions in one time if there are many more kung fu masters than cannons and are in different directions, even Tai Lung was shown to be cunning and swift enough to avoid firing weapons and was able to defeat the Anvil of Heaven, the Furious Five and Shifu on is own, Tigress hit the cannon down to the bottom floor of Tower of the Sacred Flame and Kai easily defeated many kung fu masters by taking their chi on his own. Shen must at least have kung fu skills and learn his wolf and gorilla army kung fu to defeat kung fu masters and could study and develope a dark and stronger kung fu style to put an end of other traditional kung fu styles. Kai and Taotie could make an end of kung fu, Kai easily defeat many kung fu masters by taking their chi on his own and once Taotie created a machin that easily defeat Po, Shifu and Furiouse Five (without Tigress).
Why was Shen's gorilla army also loyal to Shen if they didn't also massacred the panda village and wasn't exiled too?
Why did Thundering Rhino let himself get a blow by cannon instead of to step aside? How could the other kung fu masters survive blow from the cannon when Thundering Rhino who was easily die of just a one blow, but bigger and stronger? Po survived probably because of his enormous body fat. but Thundering Rhino was even bigger and stronger.
Wasn't most important to stop Shen from conqured China than to stop him to put an end of kung fu?
Did Shen want to take revenge on his parents? It were his parents who banished Shen becasue he want to conquer China and massacred pandas, but why did Shen still want to seek revenge when his parents was nevertheless died before his return?
Why is Thundering Rhino's physical appearance different than in Kung Fu Panda Holiday? Why is shown in the credits of Kung Fu Panda 2 Po made the the Furious Five action figures when he was a child if he was fan of kung fu since he was a teenager and the Furious Five were just formed then as reveald in Secrets of the Scroll?
Why is even shown or mentioned that Shen began his plan years before or it was lesser than 30 years ago for the panda massacre and when he was exiled if it was 20 years ago as revealed in Kung Fu Panda 3?
In Kung Fu Panda: Legends of Awesomeness, Po never went to school as a cub. However, in the credits of Kung Fu Panda 2, young Po is seen in a schoolhouse.