Final Ultima

I still say that Aizen is the villain, he wants to become God and he alone wants to stand in heaven. We even see in the flashbacks how Aizen was scheming from the start. Dude's dialouge always involves only him retaining valid information (like his discussion concerning the Royal Kings) and when he noticed something about Urahara we see the suspicious look in his eye's and not too mention the thing about Gin (Obvious recrutiment). Heck he was even hiding listening in on people's conversations.
Aizen set this up all himself fella's I highly doubt there is anyone else pulling the strings in my opinion.

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