Po, after landing in his hometown, now in ruins from Lord Shen's invasion, finally completely remembers why he lost his parents. Filmed from Po's perspective, his mom, pursued by his soldiers, intentionally leaves him in a pile of radish cartons so he would at least be spared and undetected, and before she lured away Shen's forces and he never saw her again. This is especially moving considering how, previously, Shen tries time and again to convince Po that his parents did not love him, just like he believes his own parents did not as well. The sweeping music, combined with the switch from 2D to 3D animation, and his mom's pained expression from giving up her baby, pulls at the heartstrings even more and making it hands down the saddest moment in a Dreamworks Animation film.
Ditto combined with Fridge Horror as you realise Po's line from the first movie about him eating while he's sad. His mom left him in a Radish crate that was full, and when he got to Mr. Ping's restaurant it was empty. On the bright side, it also makes his other line in the first movie, "I'm not hungry" all the more epic.
It's the little things that make that scene, like how gold is the color of heroism in these movies and Po's mom is literally glowing gold as she leads the wolves away. Or the fact that she is last seen with Shen himself chasing her down. In fact, if you listen closely, you can hear the staccato buzzing sound associated with Shen using his throwing knives...
Listen carefully when Po's mom leaves him in the radish crate. Po barely manages a "Ma" as his mom puts him there. At this point he realizes who he loves as his mother, but she has to leave in order to save him.
Even more sad is that it is implied that Po's Mother was killed. Saddeningly confirmed in the third movie.
One of the most saddening parts (because of its realism) is how, after he comes back to himself in the present, Po can only stare off into space...and then slowly, softly, sob as he breaks down, giving in to his grief as the Soothsayer urges him. Yet more proof that Jack Black really can act.
Worse, listen to the Soothsayer essentially saying It's All My Fault. She told Shen a panda would stand in his way, and she states not even she could see what would happen next.
The face of Po's mom during the whole thing. She never says a word, and yet is still able to convey so much raw emotion that it is simply heartbreaking, watching her first making a joyful, playful face to cheer up her son, clutching him one last time as she very nearly breaks down in tears, before letting go of him to distract Shen and the wolves.
Master Thundering Rhino being blasted to bits by Lord Shen's cannon.
Not to mention the followup: While Po and gang are being led to Lord Shen's palace, they come across a big groove in the ground and Master Rhino's hammer stuck upright at the end (with a large dent in it from the cannonball, no less). Whereby Wolf Boss pats it and chuckles evilly...
It's actually worse if you watch Master Rhino in the holiday and masters special's because you get to see how noble and benevolent he was before he died. The masters special even shows us that for a long time he felt as though he could never quite live up to his father's Kung-Fu legacy.
Tigress' Big "NO!" and Futile Paw Reach as Po is shot. Later, Po finding a badly injured Tigress after she took the bullet for him.
Po's reunion with Mr. Ping. Also a Crowning Moment of Heartwarming. Yes, they managed to take a concept as ridiculous as A huge panda being the son of a tiny goose and make it tug hard into your heartstrings.
What makes this worse is that Mr. Ping reassures Po before this that he will always be his father...right?. Po doesn't really reply and just leaves. The pain on Mr. Ping's face is too real to not realize how he feels.
The way Po sadly says "Goodbye." Not "Goodbye, I love you," or even "Goodbye, Dad," just "Goodbye," like he's wondering if his entire relationship with his father, who he's loved and trusted his entire life, has been built on a lie.
Watch Soothsayer's face when he first reappears: she's surprised and is actually a little bit happy - before he starts making threats.
Boss Wolf's expressions as he struggles with the need to obey his master and the need to protect his pack. It's worse when you take into consideration that he had been childhood friends with Lord Shen, and then he is thoughtlessly, instantly murdered by Shen when he decides to stand up to who had once been his friend in a hopeless effort to save his kin.
The sight of all ten kung fu masters, the most powerful and noble warriors in the land, in the aftermath of the battle completely drained and utterly defeated, seemingly without a chance in the world... the shot of Shifu watching Po- either a surrogate son or a dear friend to him- looking as if he was preparing for a Suicide by Cop makes this troper's heart break.
"My son is alive."
Makes it even sadder is that for a long time Po's biological dad had believed his family was killed that night.
Tigress when the Furious Five are all in chains after seeing Po take a shot point blank from the largest cannon in Shen's arsenal. It's not hard to see that the apparent death of her closest friend has completely broken her. The only thing she can muster when Shen comes to taunt them about their defeat is a low growl and a look of pure, undiluted hatred.
Remember, she's not growling at him because he's taunting them, it's because she believes he killed Po.
Just before Shen blows up the bridge, the chained up Five are silent and sad. Monkey is trying to encourage them to remain strong and wants Tigress to back him up. Pan to her and all she can do is look utterly heartbroken.
The novel straight up states that Tigress was crying.
Shen's normally stoic demeanor when talking about his parents breaking, if only for a moment, when the Soothsayer told him that they loved him so much that sending him away killed them. For the briefest of instants, you see a look of regret and maybe a little sorrow on Shen's face before he tries to cover it up.
Shen: My parents hated me, do you understand?! They wronged me and I, I will make it right.
In the beginning flashback, you do see Shen's parents and their reactions (at first) are of concern. When he returns, there is definite horror but also sadness. No parent wants their child to be dangerous but they had to face that.
Furthermore, just Shen himself. He was a sickly albino peacock and while his parents cared for him, there's also evidence that he was raised mainly by the Soothsayer. And like Tai Lung, everything he does is for the purpose of making his parents proud. Unlike Tai Lung, there's clear evidence Shen knows what he is doing is wrong, but he remains on the path; otherwise, everything would be for naught in his mind.
Upon seeing his parents' horrified expressions in the first flashback, Shen's expression turns from triumphant to dismayed. It looks like he honestly expected that they'd praise him for his attempt to prevent his fate through genocide.
The final battle's ending. He doesn't move from being crushed. He just seems to close his eyes and accept it. Perhaps he managed to find some peace in the end.
Before that, Shen's quietly agonized query to Po about how he could possibly go on after everything was taken from him, including his parents. He was never able to let go of the past.
Ping's freak out as he's worrying about Po will make anyone tear up. Fridge Brilliance takes it one step further, as you realize than even though Po's a giant, fully-grown panda, Mr Ping still thinks of him as a baby, like any parent would.
Mr Ping: Why'd he have to go and save China? I mean, I know why...but why? *voice breaking* He's just...one...little...panda...
Mr. Ping breaking down at the end, when he thinks Po isn't coming back, and then Po reappears.
It's a quick moment, but after Shen breaks through the barrier and sails into the harbor, Po swims over to check on Tigress, and realizing he's the last one left to stop Shen, pushes her away; she reached after him, as if to try and get him to stay.
When Po gets hit by the cannon ball, it cuts to Shifu hundreds of miles away as he falls from his staff and looks very distraught, implying he could sense what had just happened. The fact that Shifu who spent so much time of the first film disliking Po now looks completely heartbroken believing he's dead is what really gets to you.
It's played for laughs, but Master Ox and Master Croc's situation when they are seen in Gongmen Jail is sobering. They saw their friend and leader Master Thundering Rhino, who was thought to be invincible, get killed by Lord Shen's cannon, and are imprisoned in the cells of their own city, aware that one wrong move could lead to Shen turning the weapon on the innocent people of Gongmen. They know exactly what's going to happen, and they're helpless to stop it.
Master Ox: It's time to surrender, panda. Kung fu is dead.