Two things.

Aizen definitely has complete control over his reiatsu, which probably helps him greatly in avoiding being sensed by reikaku. We know that in combat reiatsu has to be exerted. We also know that unless (assuming someone has complete control over their reikaku) the person relies completely on reikaku, and just goes straight into battle, their reliance on reikaku will increase as the battle goes on. They rely more on their reikaku than they initially do over time, subconsciously. So what I'm assuming is that Aizen hid his reiatsu completely until he actually attacked his opponent. From what we've seen Aizen almost never actually engages in battle unless he's delivering the killing blow, which wouldn't allow them to sense him. Even if they did decide to rely completely on reikaku, unless Aizen exerts reiatsu they shouldn't be able to find him. So yes, that could be considered a weakness of Kyoka Suigetsu if it cannot control reikaku, because it means that theoretically they should be able to find the real Aizen and ignore Kyoka's effects.

We don't rank Shunsui with Yamamoto or Ichibe'e because he doesn't belong there, he's the next level down. Yamamoto and Ichibe'e are legendary characters, they're literally among the strongest characters in the series. It's the very top tier with them, only about 5 characters, to my knowledge, reside in that realm of power. Aizen, FGT Ichigo, Yamamoto, Ichibe'e, and Yhwach.

That said, his powers are very scary, it's a h4x Zanpakuto that basically spells for the death of anyone who's caught in it. I don't think his Bankai breaks through Zanka no Tachi, I think it's more so that it would work around it. I'd be very interested in seeing a battle between him and any of the people at the top, really. He has the reiatsu of a monster. It's a shame he had to go against Lille, literally Intangible: The Character.

/r/bleach Thread