User blog comment:Caesarea37/Chapter 556: "The Wolfsbane" Review/@comment-9096222-20131106185156/@comment-11051098-20131112133954

Everyone who witnessed the release of Kyôka Suigetsu, was forever caught in its complete hypnosis whenever Aizen released it. And a complete hypnosis isn't something one can easily fight. Aizen had at some point caught probably all former and current captains and lieutenants with it, so they couldn't easily fight him because he could control them by showing them anything he wanted.

I'm not surprised that Shinji failed, even stronger and more skilled captains like Shunsui and Sui-Fêng failed and were cut down. And despite that, we haven't even seen how well Aizen can fight without Kyôka Suigetsu's power.