This is based on opinion. Please don't list it on a work's trope example list.
Tear Jerker / Family Matters
Carl visits the grave of an innocent man who was killed during a hostage situation one year prior. He feels it was his fault since felt he didn't do anything to save the man and as the episode progressed, he was taking all of his frustrations and anger out on the family and people around him. While he's at the gravesite and apologizing his heart out, the late man's wife arrives and forgives him as they comfort each other.
Harriette: It wasn't your fault.
Carl: I know that up here...(points to head)...but not down here (points to heart).
The man's widow explaining to Carl that she understands how he feels; on the night of her husband's death, she had playfully pestered him about having a craving for ice cream, and after feigning a complaint he decided to go anyway...then the hostage situation happened. She had spent much of that year afterward blaming herself, believing that if she hadn't asked him to go to the store that night he wouldn't have died.
Harriette and Rachel reunite with their father, who they hadn't seen since they were kids. Rachel is alright seeing her dad because she was so young before he left, but Harriet got to bond with him a lot more. She's heartbroken and hurt that her daddy would lie and abandon her as a child.
Harriette: Why weren't you there when we needed you?!
Laura finding out that her campaign for a Black History class is only fanning the flames of hatred.
A note in Laura's locker: "If you want black history, go back to Africa."
Plus Carl and Harriette's discussion of racism and this whole predicament.
In order to help Laura through this, Estelle tells her a touching story of when she was growing up. She loved to read, but could not use the town library because it was for whites only. Estelle explains that the first time she tried to go in, the librarian pushed her into the street. She went back every day for six months, enduring staring, name-calling, and spitting, until one rainy day, the librarian shook his head and handed her a library card.
Estelle: And, from that day forward, everyone could use that library.
Waldo's defeated, repeated, "Aw, gee," when Maxine mistakes Eddie's messing around to mean that Waldo is too, and you see how broken up he is when he thinks the girl he loves hates him.
Good thing they get back together thanks to the two girls who Eddie invited over helping to clear things up. You even find yourself cheering when the girls become disgusted by Eddie's unsympathetic attitude.
A Real Life one. Michelle Thomas, who played Myra, was struck with a rare stomach cancer during the eighth season, which was why she appeared so sporadically during the final season. She put off some of the more extreme treatments because she wanted to have a family and the treatments would have rendered her sterile. She died only a few months after the series ended.
There is another meta Tear Jerker: This show was an instance of the cast finding out the hard way that the sets were destroyed and the series was cancelled.
One episode has Steve and Carl sharing a hospital room—Steve has appendicitis, Carl got shot in the butt. (Yes, really). After characteristically annoying Carl beyond all reason for the whole episode, Steve saves his life. It turns out the "doctor" overseeing Carl's case was the angry sibling of the criminal who shot Carl in the butt, whom he arrested. Later that day, the family comes to visit. Laura stays behind, hugs Steve, and tearfully says, "Thanks for saving my daddy."
Any interaction wherein one of the Winslows tell Steve off or otherwise finally exhaust his ability to take their shunning. The sleepwalking episode gets special mention because Steve needed a hypnotist to get to the bottom of things.
This also applies to any time someone calls Waldo an idiot or otherwise seriously dents his self-esteem.