The most depressing anime scene had to be in Death Note.
First of all, this anime was a masterpiece. It was brilliant, original, intriguing and vicious! And, there were many scenes that surprised me to the point of depressing over it. If you think about it in a sense of the whole anime being around Kira vs L, it is not easy to pick a side since everyone likes both characters. So obviously many deaths were tragic!
The most depressing scene, for me, came at end. When everybody was at the warehouse and discovered Kira’s true identity. He had been defeated, exposed and had no way out. He was lying on the ground, crying and shouting, and could not believe his situation. Power corrupted him. He could not accept defeat. And there is nothing more pitiful and depressing then not knowing when you have lost.
To watch a character, who you admired and hated, pass the point of embarrassment and humiliation like that is impressive. And, the scene lasted for a couple of minutes to intensify this effect.
Original question and answer: https://www.quora.com/What-is-the-most-depressing-movie-anime-scene-you-have-ever-watched/answer/Afas-White?share=2d2fcdfc&srid=hFWM6