Po accidentally destroys a village with a Power Fist while fighting Klaus and Veruca.The consequences that follow make the second half of the first episode depressing.
Po gets kicked out of the village he was trying to protect. All Po wanted to do was eat dumplings, but he ends up destroying a village by mistake.
Po's dejected travel back home. All of the citizens who greeted him in the first half look at him with scorn, making him feel more depressed.
Upon returning home, Mr. Ping tells Po that his title as Dragon Master was removed by the Emperor of China for what happened at the village. After watching Po's journey to prove himself worthy of his titles, it's heartbreaking to see him lose it.
Po having to betray the trust of a group that believed in him in order to continue the mission.
The head monk’s reaction was heartbreaking as well.
Wandering Blade leaving Po at the end of episode 4 after telling Po that he can’t be her friend as the mission is more important.
Despite abandoning him to die to sake her own skin, Veruca has a total breakdown when she discovers that her brother is still alive and has abandoned her, she even looks around her undead army looking for him to make sure this isn't true.
After Veruca is stabbed by Alfie, her brother who has taken residence on the island with the other mage senses her death, despite Veruca leaving him to die to save her own skin, Klaus still didn't wanted her to die.
Even Po appears to be saddened by her death as he covers her body with a blanket.
