Since someone who is definitely above all of the captains except Yamamoto, Isshin, said Aizen was on a level so high that he could not feel his reiatsu, I'd say that Yamamoto would be the only other person, besides Ichigo, that could have felt his power.
That said, Ichigo and Aizen were on a level so high that there is no comparison to Yamamoto.
Here's the difference:
When Yamamoto flexed his reiatsu, a Lieutenant had difficulty breathing. When Aizen LOWERED his reiatsu, objects that touched him disintegrated.
Here's how Aizen's power was described: he was so far above those around him, that they could not feel his power.
Ichigo was so far above Aizen, that Aizen could not feel his power.
Everyone can feel Yamamoto's power so he's no where near as strong as Aizen's first transformation.
So we are talking about a gigantic difference in power. Several multiples. Ichigo's strikes were destroying mountains just from the shockwaves, alone.
Originally posted by Nephthys
Actually he couldn't feel him because he transformed all his reiatsu into physical might iirc.
You're probably right but I just got done watching the anime and that was the reason Aizen gave and he started getting "pissed" and losing his sh*t over it.
I thought that explanation was really good. SOMETIMES, the animes do better at explaining things than the original writing. Not always...but sometimes.
Originally posted by Nephthys
Actually he couldn't feel him because he transformed all his reiatsu into physical might iirc.
And once Ichigo transforms, Aizen realizes he was wrong. It's because Ichigo had attained a higher level of 'Transcendence' than Aizen had.
I still find it stupid on how Ichigo was able to gain more power from mastering his Zanpakuto, than Aizen did from subjugating the Hogyoku.
Though it's a pity Aizen never resorted to his Bankai.
Well more physical power surely, but remember that Aizen won that fight because he could still regenerate at the end. Frankly the FGT kinda sucked. One attack and then you lose all your powers. 😬
I would have loled if Aizen had just flashstepped out of the radius and it turned out that Ichigo had just completely blown his load.