9. Yu Yu Hakusho - Yusuke Urameshi
What makes Yusuke's death so surprising is the fact that it occurs even before Yu Yu Hakusho's first episode finishes. Talk about a hook. Not many shows are brave enough to kill off the main character in their first appearance.
Of course, this being anime meant that Yusuke's death doesn't quite stick! Regardless, going into Yu Yu Hakusho for the first time, seeing its upbeat opening song and comedic nature makes it all the more jarring how dark it gets almost immediately. A 14-year-old boy dying and believing that no one would even care if he died is especially tragic.
Witnessing this delinquent boy who skips school, gets into fights, and accidentally mugs people selflessly giving his life to save a random child leaves quite the impression; to make matters even grimmer, his ghost is led around spectating everyone impacted by his death.
From the principal, he always caught flack from remarking how much of a shame it was, childhood friend breaking down in tears, his rival begging for him to come back and fight him, we witness all of this. What's most heartwrenching is the scene of his own mother acting almost catatonic until eventually bawling in anguish.