SS2 Vegeto

I'll try to wrap this up (as if..it wasn't). Aizen explains in detail the limits of shinigami. Seeing as you can be precisely twice these, as later revealed by statements about the hogyoku (discussing requirements for full power premature awakenings), then it is indeed a general limit. After a detailed explanation, Aizen then asks the retorical question - once you hit these limits, can you pass them? He responds that there is only one way. To become a hollow. He explains the hogyoku's ability to remove the barrier between shinigami and hollow. Why would he bother explaining all of this in such detail, if it didn't currently have any relevance to him? It is at least strongly implied by this that he has reached the limits of shinigami. In fact, later, on being questioned of his purpose in forming an aliance with the menos, he responded "to reach greater hights". I think it paints a pretty clear picture. If Aizen has reached the limits of shinigami, then the only way that Urahara would be able to outmatch him is if he had surpassed those limits himself - of which we have no evidence, making it a baseless argument. And for the record, Ulquiorra thought it would be trouble fighting both Urahara and Yoruichi, at the same time.

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