This is based on opinion. Please don't list it on a work's trope example list.
Tear Jerker / Log Horizon
Episode 19: Rudy's Heroic Sacrifice. His party members gather around him to cast one revival spell after another only to be baffled that nothing works. Then Izuzu reveals that he's a lander and that he's going to die for real, while blaming herself for not stopping him for going into dangerous situations.
Season 2-whenever Akatsuki has an internal monologue about missing Shiroe and/or how she feels useless. It builds up through the episodes until it reaches a climax. The serial killer kills her and her last thoughts are about Shiroe.