This is based on opinion. Please don't list it on a work's trope example list.
Tear Jerker / Life In 16 Flavors
In Chapter 3, Choko recounts what it was like to witness Turbo's destructive hacking from within the game code itself. Particularly heartbreaking is how she tried — and failed — to help the NPC King Candy, which becomes even Harsher in Hindsight when the original is restored to life by the reboot and is revealed to be a Mean Character, Nice Actor.
Vanellope's breakdown in Chapter 5 after she discovers Sugar Rush was devestated by a virus and crashed, with all her friends corrupted and suffering horrific glitches to the point of being unrecognizable.
Ralph's reaction to having to watch helplessly as Vanellope races Virus-Van, followed by Sugar Rush resetting right before his eyes. This is immediately followed by him racing to the game and tracking down Vanellope, only for her to have the doughnut guards escort this 'stranger' right back out.
The other effects of Vanellope forcibly resetting Sugar Rush are also tear-inducing:
Minty Candlezaki and Sour Appleblossom becoming heated rivals, practically out to kill each other. (As well as the small but telling detail of everyone calling her 'Minty' instead of 'Candle'.)