Re: What was Aizen's backstory?
I refuse to believe his backstory is so simple that it was because he was 'too strong'.
Aizen appeared to have a strong hatred towards the Soul King; even referring to him as a 'thing', and believed the world wasn't the right way. He was also extremely obsessed with unifying the different species.
My belief is the Aizen simply believed in equality, he wanted everything in the world to be equal, meaning everything would have the same power he did. But when Ichigo surpassed him, he refused to believe that it was possible for greater power to still exist, fearing that eventually he'd be overpowered by everyone else. Ichigo was close to understanding him, but didn't completely. I believe Aizen hated the Soul King simply because he didn't believe in hierarchy, and to change it, he'd have have to destroy the Soul King so all things could crumble, and he could rebuild it. But subconsciously, the real way for Aizen to feel this equality, was for him to lose his power and simply go back to being among his fellow Shinigami.
If you can't keep up with what I'm saying, then 421 and 422 will be a good re-read.
I for one, am excited to learn more about Aizen.