Please don't list this on a work's page as a trope. Examples can go on the work's YMMV tab.
Tear Jerker: Homicide: Life on the Street
Giardello's speech at the end of "Partners and Other Strangers".
The scene in "Every Mother's Son" when the mothers of a murdered child and the boy who did the killing meet unaware of who the other is.
The scene in "Crosetti" when Lewis realizes that his partner and friend committed suicide.
"A Doll's Eyes" when the parents have to take their son off life support.
Charles S. Dutton's performance in "Prison Riot" especially his line "I'm in here forever, Detective. Forever."
The end of "Blood Wedding" and "Betrayal".
Lewis talking Kellerman out of suicide.
"Bop Gun" particularly the ending.
Bayliss' shooting in the season 6 finale, "Fallen Heroes". Just all of it from Pembleton's reaction to the look in Bayliss' eyes (and his eventual seizure) to the former's breakdown in the hospital, begging God to let his best friend live.