This is based on opinion. Please don't list it on a work's trope example list.
Tear Jerker / You're Under Arrest!
"The stopwatch that was once soaked in the rain was now soaked with tears." Watch it.
Also the end of the episode featuring Yoriko and Prince Saki Abdusha. Specially when she rejects his marriage proposal due to their age and class differences, but still goes to the airport to say goodbye to him as he goes back to his war-torn home to try bringing peace to it, and cries silently when he boards his plane.
And the end of the first episode of the "rogue officers" two-part, when Nakajima breaks his leg while trying to catch the Face Heel Turned policemen and lays in incredible pain on the ground, and next to his totalled bike. The sadness doesn't disappear in the second episode where Miyuki has a thankfully brief Heroic BSOD and the other officers, normally rather nice and peaceful people, are so incredibly angry that they're willing to break rules and go after the culprits, screaming that they need to do it "to avenge Nakajima". The contrast with the rest of the series is so damn... stark.
The ending of the second part makes it even worse: the officers are forced to lead the rogues into a trap to take them down. Nakajima and Natsumi literally kick the two on the bikes and send them to the hospital, while they lead the one driving the car towards a barricade in the Rainbow Bridge and into a (seemingly) fatal crash. The soundtrack in this scene seems to make emphasis on the sadness on how far they had to go to stop the rogue officers.