This is based on opinion. Please don't list it on a work's trope example list.
Tearjerker / Batman: Arkham City
Joker's death. He was a terrible, lunatic murderer, and anyone who says that he deserved to die has a solid argument. But the magnitude of the situation, the slow pacing, the quiet credits, and what happens in the middle of the credits, there's such an emotional impact. And when you realize that this may well be the last time we hear Mark Hamill's Joker, it really does feel like something important, something you've known since childhood, really did die.
And it's not just his death, but his final moments leading up to it. Right after his last laugh and his Incurable Cough of Death, his body suddenly starts jerking as he clutches his chest and makes very loud, painful gasps, indicating that the Titan poisoning has completely taken over his bloodstream. The gasps start slowing down and getting quieter as seconds pass, until, at his final gasp, he quietly lets out his long, last breath as he goes out with a smile. Combined with Nightmare Fuel, nothing says "painful sadness" like his last moments.
What really makes you wanna cry is how none of the Joker's gang attacks Batman when he carries Joker's body out of the theater. They all just stand back, getting out of Batman's way, and watch, shocked (and appropriately so).
You hear his gang cheering "JO-KER! JO-KER! JO-KER!", but when Batman carries out his body, it just... stops.
Heck, the music alone is enough to make you weep. The name of the song in the soundtrack? Four words: It's. Not. Even. Breakfast. The song starts seemingly normal and dependent, but then shock starts coming in at around the 1:20 mark. Over a minute of unease starts settling in, and then, at around the 2:35 mark, the waterworks start on emotionally. Truly a Crowning Music of Sadness. Give it a listen.
Knowing that this would be the last time Hamill would voice the Joker, "Only You (And You Alone)" feels as much like Hamill singing his farewell to his fans as it does Joker singing to Batman. It's a beautiful send off for this era of the Joker.
During the Playable Epilogue, walking up to any of the Harley statues and activating it plays her message: sobbing uncontrollably.
Watch the reactions of the members of the Joker gang gathered around the theater as Batman walks out carrying Joker's body. Harley just... collapses.
One of the Riddler's interview tapes has him imply Hugo Strange has a Batsuit hidden behind a secret panel in his office, that he sometimes wears in private, sobbing into his hands and wondering if he's really worthy to replace Batman. It does a good job of hammering home how, despite his bluster, Hugo Strange is a pretty pathetic person.
Or, in another frame of reference, how unbelievably strong Batman is, to have kept it up for so long.
The scene as a whole beautifully describes just who and what the Batman is, a terrifying creature whose sole purpose is to prevent the very thing that created him. One can't help but shed a few tears as Bruce/Batman mourns in what is one of the most poignant scenes in the game.
Batman's hallucination of his parents standing behind a white light when he's close to death from the Titan blood.
Immediately afterwards, Oracle freaks out as Batman is only minutes from death and begs him to tell her what to do, what to tell Robin. His reply is that he'll make it.
The death of Talia al Ghul. The pain in Batman's and Talia's faces as she dies is pretty sad. Joker'sKick the DogToo Soon line is somehow both funny and enough to fill a player with hate-filled vengeance towards the villain due to the sadness of that scene. Talia probably isn't Killed Off for Real because of the Lazarus Pit, but it is still sad.
Harley's pregnant. While this first seems like good news for her, there's a lot that makes it very likely more of a Tear Jerker. Considering the baby was conceived while Joker was sick, if the Titan has the ability to be based on to offspring, the baby could easily be deformed in some way; it's more than likely that the baby will be taken away from Harley after it's born; and, worst of all, who's to say she'll even give birth to it? The pregnancy test was no doubt taken sometime before the start of the game, and she couldn't be too far along. A lot of the things that we can assume happen to her could have resulted in miscarriage. Plus the possible Titan-based damage present in the baby itself could cause the baby to die before it's born. And the whole premise in general is pretty sad: Harley is in an abusive relationship with the Joker. Instead of the baby "bringing them together", which is sometimes the sad logic of some abuse victims, the baby might well wind up as another victim of Joker's.
Titan isn't the only thing in Joker's body during Arkham City. He's always had traces of the original Joker Venom in his veins, as well.
The new DLC hints that the pregnancy test might have given her a false positive. This coupled with the fact Joker's dead and she has a gang she has no idea how to run (and none of them can stand her), is tragic in its own way, psychopath or not.
Freeze: Have you ever seen a flower die? Watched something that was once so beautiful, so full of life, collapse and rot from within?
Mr. Freeze in general.
Do you know what the title of his boss theme is? "Bring Her Back To Me." Ouch.
After you defeat the Mad Hatter you can enter his lair where Batman will tell him never to mess with his head again. The hatter replies that all he wanted was a friend and bursts into horrible sobbing that is truly heartbreaking to listen to. Listening to his interview tapes, he is a killer but it is also obvious that the poor man is completely delusional and needs serious help which he's not going to get. Hearing Hugo Strange manipulate the poor bastard into helping him is also horrible.
When you're in the museum and you see the exhibits Penguin has set up. One of them contains the taxidermized hyena pets of Harley's/Joker's. Harley LOVED her babies, and Penguin just murdered them and set them on display.
The gloomy music outside the Steel Mill in "Harley Quinn's Revenge" is more depressing, as it takes on a whole new meaning after the Joker's death by Titan poisoning.
Also, when Batman speaks or thinks to himself in the flashback, just hearing him is more depressing, as you can hear the pain, tiredness, anger and sadness in his voice. It's like he hasn't sounded the same as when the Joker was still alive. In fact, it's almost like he hates himself for breathing without the Joker, as if he may never get over the death of his greatest enemy as well as that of Talia. After all that he has gone through, you feel like you wanted to give him a hug so badly.
The ending of the comic Arkham City: Endgame. Just before the process of cremation, Batman takes one final look at the Joker's corpse. Losing the Joker to the disease has taken its terrible, emotional toll on the Dark Knight for so long, and it's taking a long time to heal and find closure; but in the end, he finally learns to let go of the bond between them and move on by saying his last goodbye to his longtime foe. So emotionally sad that the Clown Prince of Crime is truly never coming back in the Arkhamverse, but, in the words of Madonna, there is no greater power than the power of goodbye.
"No more laughs."
Harley's behavior in the DLC. Thanks to Joker's death, she has definitely gotten crazier, more dangerous, and more ruthless. And yet, it's still incredibly sad to watch. Now, her behavior is not justified at all but you can definitely see why she is acting the way she is. After all, she lost the Joker, who is more or less her entire world. And some people just can't cope with losing their whole world. It all gets even worse if you have ever lost a loved one of any kind.
Harley:Oh, Mr.J. Why did you leave me? What did I do?
There's a scene in the prequel comic where Aaron Cash is forced to send his favorite inmate, Jimmy Briggs, to Arkham City. Briggs never harmed anyone (unless in self-defense), always followed orders, and was only at the asylum for having delusions. Jimmy begs not to go, and Cash helplessly says it's out of his hands.
Aaron Cash: "I'm sorry, Briggs."
Catwoman's flirting with Batman comes off as sad. She clearly cares for him, pines for him, but feels like he doesn't reciprocate, and believes he must be spoken for. It's sad because he's involved with Talia this game, but Selina's bio mentions that she and Batman have romantic history, and he still flirts with her somewhat, leaving that little strand of hope dangling for her. It comes across as even sadder when you're listening to her interview tapes with Hugo Strange.