 If you liked
Cross Ange: Tenshi to Ryuu no Rondo
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 ...then you might like
Kidou Senshi Gundam: Tekketsu no Orphans
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Apart From being a mecha anime , Both of them have some similarities, Both the anime present a dark situation where the main character has ended up in a Tragic Situation, Where his life is threatened.
Both anime present a Prevailing group of outcasts who need to be stopped and exterminated.