ISSHIN & ICHIGO - to protect 100thousand soul from being made as the King's Key
GIN - was completely uncomfortable with Aizen when destroying Koutotsu
RANGIKU & KIRA - maybe to save Gin
URAHARA & YORUICHI - he did frame Urahara for holowification and made them live in exile
HITSUGAYA & HINAMORI - Aizen completely fooled Hinamori and even trick Hitsugaya into stabbing her too so Hitsugaya should strike the final blow
SHINJI & HIYORI - let alone events happen to the Vizard 110 years ago Aizen (actually Gin) add salt too injury by bifurcating Hiyori
KOMAMURA & HISAGI - Aizen make Tosen explode
BYAKUYA, RENJI & RUKIA - it is Aizen plot that nearly kills Rukia in the first place
ORIHIME INOUE (new addition) - she did stated that her power are the only one who can bring back the the result from the hogyoku power to its previous states (but not kills Aizen but only to weakens)
OTHERS - KENPACHI ZARAKI???
Why? Who do you think would make such a compelling case to earn the rights to just kill Aizen? Surely it is obviously Ichigo - but previously if the fight was still on FKT he have no reason whatsoever to kill Aizen but now he must protect the real town with his father. The others have their own rights too - anyway if you have different opinions just let it ripped here we'll see how this turn out to be...