Aizen appearently has a setup that makes Aerial I a garunteed hit.
The setup is very short and easy but is also very good. All you have to do is have the opponent block an Aerial J and then immedietly do Aerial I.
The opponent is unable to avoid it in any way once they have blocked the Aerial J unless they Quiet step right after the Aerial J. If the opponent does not quiet step on time they will get hit by the Aerial I. This setup will not work if your opponent is cornered.Here is a gif for the setup: https://gfycat.com/RapidWaryDeviltasmanian
EDIT: After some more testings, for some reason this setup only works on High or Best quality settings.