This is based on opinion. Please don't list it on a work's trope example list.
Tear Jerker / Before Watchmen
The final issue of the story where Blake crosses his own personal Moral Event Horizon and kills Bobby Kennedy, one of the few people he loved, to keep him from talking about Vietnam and especially Blake's role in it. He then calmly dumps the gun, gets into his car, slams his head into the steering wheel and does nothing else.
Silhouette storms a meeting of pedophiles watching child pornography. Originally she was going to scare them, but she begins to straight up murder them when she finds a girl amongst them, eyes dead, and demeanor unmoving. She grabs the girl and runs out, before being shot. The bullet goes through her back and into the girl's heart killing her. Ursula's main thought was how her eyes didn't change throughout the process, assuming she's been "dead" for a long time. When Ursula is rescued from the church by Hollis, her first thought is for the child which Mason tells her is dead.
When she was shot, she mentions that the girl is fading from her, just like a flickering light. The following panel has a simplified Ursula and the girl as part of a light bulb, with the girl falling away from the center. The flickering light bulb and near death experience could be foreshadowing for her own death, which we find out is in the very next issue.
Silhouette killed. You knew it was coming, and the event was foreshadowed, but when it finally happens, she's hunted down, and brutally sliced and stabbed to death when trying to protect her partner, Gretchen.
The issue has a number of points for her when her backstory is revealed: losing her sister to the sadistic Rolf Mueler, and fleeing with Gretchen to America, "running from a past they never could escape."
As well as the point where she's outed, and kicked off the team despite Mothman and Nite-Owl's best efforts. She doesn't even get a proper funeral, just buried with Gretchen with two unmarked stones, with Byron and Hollis the only ones in attendance, though Sally and Eddie come later.
Eddie of all people shows he has some empathy when he comes to the graveyard to pay his respects and talks to Sally about his time in the Pacific. His unit was all killed, save himself and another man named Greg. A native woman found him, and she and Greg took him to her home, where she patched him up. When the two leave, Eddie even gives her son his helmet. The General Ripper in charge orders the area shelled when he gets back. Eddie tries to warn her, but comes too late, finding her badly burnt, with her son a fried husk fused to her side. The General shoots her in the head to put her out of her misery.
Dollar Bill's death, we knew he was Doomed by Canon, but here, we just see him lying on the ground, propped up, with a longing expression on his face. Hollis mentions that yes, getting one's cape caught in a door and being shot can be funny, but he also states that Bill was his friend, and he's sad to see him go.
Bluecoat and Scout's backstory. They're a Japanese father and son who are trying to stop Scout's grandfather from blowing up the statue of Liberty. They, and many of the terrorists, were victims of the U.S. internment camps, where Bluecoat lost his wife and Scout's mother. Upon trying to stop the plot, Bluecoat is killed, and Scout saves the statue, by preventing the radiation bomb from going off; however, he takes a full blast of it to the face, and dies an agonizing five day stay in the hospital, horribly disfigured by tumors. Their act of Heroism was covered up by the Government because they didn't want to look bad.
Hooded Justice's death. After what we find out about him in issue 5 that he's the child killer, it's hard to feel bad for him when Hollis breaks his neck to prevent Byron. Then Cooke pulls his twist, and shows us that what he did was a classic vigilante act, without full evidence by Comedian admitting to kidnapping the final kid dressed as Justice to trick him, though he didn't expect Hollis to kill him. Hollis remarks that Justice would have killed him and Byron that night, but it wouldn't have come down to that if they'd known.
When Hollis gets his Berserk Button tripped leading to the above incident, his thoughts go to Moe Vernon's song, "Ride of the Valkyries", which he played when he committed suicide after finding his wife was having an Affair. He also sees Silhouette's Nice Hat, laying upside down next to her blood soaked bed.
Then there's Justice's "funeral." Nelson blows up his base, the place where they all hung out, and plotted to rid the city of crime, their own hangout, and the building he was so proud of to cover up evidence, or honor Justice's death, Mason doesn't know which. Nelson can just be seen there, holding his hat to his chest, crying.
There's all the implications surrounding Hooded Justice: we never see his face outside of shadow, and he's implied to be the boy from issue 4, taken by Rolf Mueller to live a life under the sadistic Nazi pedophile. It's implied the Hood stays on to prevent him from showing his face, something possibly due to the sexual assaults.
Byron's gift. After all the years and throughout the issues, he's been degrading under paranoia and alcoholism, to the point where issue 3 has established that in the "present" he's catatonic. Hollis reveals that he was the one who bought him the Garage he now works in, and fixed the place up, Hollis hugs him because he knows that this last act is his goodbye, as his last act of clarity before breakdown.
After Comedian's revelations, Hollis burns the pages of his book that we've been learning over the past 5 issues, to hide the truth and protect the survivors. He does so at Ursula and Gretchen's grave.
When Moloch is a crime boss, one of his prostitutes who slept with him admits she had an abortion, and didn't want to give birth to anything from him. Moloch is crushed when he hears, but instead of getting revenge, he gives her money and puts her on a train out of town.
Hollis' speech at the end of issue 4, especially when he decides the only thing that matters is whether or not "you go down swinging".
The first two issues are a Hope Spot. Laurie runs away from her mother and lives in San Francisco with her friends and boyfriend. Then issues 3 and 4 happen and are made all the more heartbreaking after so much happiness.