This is based on opinion. Please don't list it on a work's trope example list.
Tear Jerker / Sonic Adventure 2
"Maria...this is what you wanted, right? This is my promise I made to you."
The Last Story ending, with Shadow's Heroic Sacrifice when he uses the last of his power to warp the falling Space Colony ARK back into orbit using Chaos Control— as shown in the page picture.
Shadow: Maria... this is what you wanted, right? This is my promise I made to you.
During the final battle, there's some of this on Sonic's end as well. As the fight progresses more and more towards the time limit, Sonic begins to realize that there's something wrong with Shadow: that he's losing power, which ultimately leads to his near-death. Unfortunately, given the current situation —the five minutes until the planet is destroyed, and all— there's not much he can do to provide direct aid.
Sonic: Shadow, your power's getting weaker! Hey, are you okay...?
Sonic: At this rate, you won't last! Get back to the Colony!
What also makes it tear jerking is the people of Earth realizing that they're saved, they're not going to die... and then they all cheer him.
The closing cutscene after the True ending to Sonic Adventure 2 gives closure and underscores the tear-jerking nature of Shadow's heroic sacrifice. Three words: Rest easy, heroes.
Sonic: He was what he was— a brave and heroic hedgehog, who gave his life to save the planet.
As narmy as the theme songs are in SA2, it's kind of sad listening to the full version of Unknown from M.E. (Knuckles' theme). Though there are obvious offenders ("But every time he looks for the sun can't find it") the worst line is rather difficult to make out the few times you hear it: "Freedom will be waiting when serenity is restored". We never really get the idea that Knuckles resents the whole 'guardian' thing in-game (A little in the original SA, but not here.) but there are a few other lines that reference 'fighting for his destiny'. It's a little depressing to think that he may be fighting for freedom from his duties when it's quite obvious that it's not going to happen. Of course, the lyrics switch focus so often that it's easy to forget the above.
Amy reasoning with Shadow to save the Earth—
Amy: I know that people fight over the most trivial things. Some people may be selfish, like the Professor said... but they're basically good. If they try their best and never give up on their wishes, they always have a reason to be happy; that's why you should help them out! Saving them is a good thing! Shadow, I beg you, please do it for them! Give them a chance!
And then when she does get through to him after she unknowingly reminds him of Maria, he's seen shedding a Single Tear as he hurries off to aid Sonic and friends in stopping the Space Colony ARK from falling.
SA2's ending, if not for Shadow's sacrifice, then for the heroes and villains' conversations with one another. Tails and Eggman's heart-to-heart, in particular —
Eggman: When I was a child, I looked up to my grandfather for all the great things he accomplished in his life. He was my hero, and I wanted to be a great scientist like him! But... did he really mean to destroy us?
Tails: I dunno, but what I do know is... we all did it together!
Eggman: (fondly) ...you're right.
For True Story, the boss music during the second Sonic vs. Shadow battle at Space Colony ARK, is narmy for sure, but if you can look past that, it's also very sad, since it paints a picture of Shadow's bleak despair. Stars don't twinkle, the moon doesn't shine, stars don't twinkle, the moon doesn't shine...
Sonic's goodbye, especially since he was unknowingly echoing Maria-
The backstory of Shadow was quite sad: he had a happy life that was taken when the government stormed his home and killed everyone there, under the pretense that he was a danger to everyone. He watched Maria (essentially a sister to him) die in front of him, and his "father" Gerald was arrested, went insane from grief (a Tear Jerker in of itself) and was executed. And then they locked him away for 50 years, of which he was likely conscious the whole time.Shadow really needs a hug.
And the ride doesn't stop there, folks. Not only was he sealed away right after a traumatic event, but according to Gerald, his mind and memories had been tampered with to make him believe Maria desired revenge for her death rather than for humanity to live on peacefully. Imagine what it must have felt like to go to sleep one day mourning your best friend and wake up the next with a sudden, inexplicable-yet-unquenchable lust for revenge. With how much Shadow recollects on his memories of Maria and how zoned out and depressed he gets about it, you almost get the impression that he KNOWS something is wrong with the whole scenario, but can't bring himself to not respect(What he thinks is) his friend's dying wish. Amy talking some sense into him and helping him remember Maria's true wishes becomes even more of a heartwarming moment with all that in mind.
In some ways, the Biolizard can be seen as this. It seems to have trouble breathing, needs to pause every once in a while to catch its breath, and relies on a life support machine to survive. It's almost a mercy kill when the heroes finally put it out of its misery.
When a Chao dies, a short funerary-sounding jingle plays. In addition, this game removed the Chao's ability to die through running out of HP by being hurt by player attacks. A Chao will only die if its happiness is too low at the end of its life. While a Chao's decision to reincarnate is visible through its the color of its death cocoon in the rereleases, on the Dreamcast version a Chao will be looking down and shaking its head if it is going to die. It's not hard to intepret it as Death by Despair.
In Chao World, there is the option where you will have to send your Chao through the Chao Transporter Machine. As you choose to send your Chao away, the description reads "Your Chao will live a happy life in a faraway forest. You will never see your Chao again." The music that plays makes it even sadder. Listen for some major waterworks.
Regarding the Chao Transporter Machine, the HD version of the game takes away its menu options except for the Good-Bye option (mainly because of the absence of the Game Boy Advance link). Now it's simply named the "Chao Departure Machine".
Oh how depressing and tear-jerking the "Fake Emerald" Scene was... Let us count the ways.
Amy being held at gun-point, helpless.
The sudden realization by Tails that Sonic is in grave danger.
Amy's reaction when Sonic "dies" inside the exploding capsule. Just listen to the way she says his name when she realises that her crush has apparently been killed, before breaking down in tears.
The battle against Eggman as Tails, especially since he's fighting the man who killed his brother.
Tails: For the first time, Sonic asked me to do something for him... I won't let him down! I WON'T GIVE UP!
Switching roles, after you defeat Tails as Eggman, Tails utters the line "Forgive me... Sonic...". That gives you the impression that he has failed to avenge his best friend, whom he fully believes has died.
Eggman finally got his way.
Even though he is ultimately responsible for setting up the major final obstacle and setting Shadow on the path to complete it, Gerald's story is tragic when you realise he only did all this after G.U.N destroyed his life, killing people he worked with as well as his uninvolved and hinted to be terminally-ill granddaughter, imprisoning him to continue his work under their supervision and ultimately sentencing him to death.
Gerald: I plan to give you a taste of my revenge, once all the seven Chaos Emeralds are collected — once I initiate this program, it cannot be disabled. All of you ungrateful humans, who took everything away from me... will feel my loss... and despair.
G.U.N. Soldier: Is there anything else you want to say?