 If you liked
Kara no Kyoukai Movie 3: Tsuukaku Zanryuu
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 ...then you might like
Satsuriku no Tenshi
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Both animes deal with death, suicide themes, and more importantly, if violence is ever justifiable. Equally dark content or 'lingering' darkness after you watch it, though Satsuriku no Tenshi has more energetic characters, while Kara no Kyoukai has more reserved, mature, characters.