This is based on opinion. Please don't list it on a work's trope example list.
Tearjerker / The Hogan Family
The Aesop mentioned on the main page, regarding the episode "Leave It To Willie." The episode doesn't end happily, nor with Willie sulking over whatever punishment he's incurred, but with him sitting alone in the kitchen, crying as he realizes the impact of everything he's done.
When original series star Valerie Harper was fired and her character McLeaned in 1987, several stories during the following season (Season 3) focused on the family grieving the death of her character (also Valerie). The one that made the most impact by far was the episode "Burned Out" (financed and sponsored by McDonald's, who helped with the set damage), where a fire starts in the attic and eventually severely damages the house. The fire destroyed many of the family's possessions, but the piece bringing about the most tears was the charred remains of a photograph of Valerie. After being allowed back in their home and investigating the ruins, David goes into his room and finds the burned photo on the nightstand, immediately breaking down in tears; Sandy comes in and, comforting David, shares his grief.
Late in the episode, David reveals his emotions on the night of the fire. He had been returning home from a date when he found his street blocked off for a house fire; when he realized that it was his house, he is initially prevented from finding his family, before breaking free from a police officer and eventually reuniting with them. In the moments in between seeing that his house was burning and finding his family, he admits that he was scared that his family was trapped inside. He tells his family that as he ran toward the house, he prayed: "Dear God, I just lost my mother. Please don't take them too."
Overall, the episode was highly praised by critics and viewers - not only for the safety aspect but presenting a reality some families face in dealing with grief: losing a loved one, and not long thereafter a fire destroys most, if not all, of the momentos of that person.
The fifth-to-last episode aired in December 1990 and titled "Best of Friends, Worst of Times," details David's best friend Rich being stricken with AIDS. Throughout the episode, David and his other close friend, Burt, help Rich live out his final days to the fullest. By the end of the episode, David (along with Sandy, who at this point in the series is vice-principal at the local high school) is invited to speak at an assembly about HIV and AIDS. David touches upon his experiences with Rich, dispels common myths associated with the disease and how to prevent it... and fights back tears as he reveals that Rich had died one night earlier.