@taichokage: I don't think base Aizen has a chance of taking on Hashirama without KS
First show me a scan of him busting a mountain. Next show me a scan of him tanking a mountain buster.
Actually, Mountain level would be downplaying. Even Ulquiorra is City/Mountain level.
I'll explain something about attack-potency in manga since people here are making severely flawed analysis and taking everything at face value.
Ichigo's and Aizen's swings are supposed to be City/Mountain++ at the very least. Their shockwaves can vaporise mountains. Well, Aizen disintegrates, Ichigo completely vaporises.
A shockwave is so much weaker than the actual impact, that you'd laugh at the difference (hope you've heard of the inverse square law). The energy starts dissipating exponentially the further it goes from it's origin.
I could easily say that Ichigo destroying a mountain that's far away without making contact equals destroying several mountains at point-blank. Here we have it,
Here you have Ichigo tanking Aizen's swing with only his fingers- http://manga.starkana.com/151/5699/12.png. It does absolutely nothing to Ichigo, but creates a mountain sized crater behind (and all this was caused by just the air pressure released by the swing).
Yet Aizen's Fragor burns his arm- http://manga.starkana.com/151/5700/14.png Multi-mountain level, at least.
It doesn't matter how small the AoE Fragor if it could destroy only a house or your bathroom, it has multi-mountain level potency for the simple fact that it burned Ichigo's arm (the same guy who tanked Aizen's swing with his fingers).
Moreover, Aizen can use all six heads to form a ring with six times the power of one Fragor
Multiplying it by 6, its pretty much Island level.
@Whats_out_the_bag: Here you have them.
How the hell does that compare to this?
That's Hashirama surviving a multi mountain slice
People overhyping on that small feat of Aizen's because that feat wasn't close to actual Mountain Busting, Say for the least, Aizen sliced only a small mountain or possibly a hill because look at its size compared to other Mountains.
If this is Aizen with the Hyogoku, then Hashirama would win with mid difficulty. But if this is Aizen with KS then he would possibly win via absolute hypnosis.
Again, why would Hyogoku Aizen win?