What is Itachi Uchiha's potential?

[Claraviolet]

So, if Itachi somehow defeated that illness....do you think he could have become even stronger?
I wonder how strong he is without that damned illness.

 

[Kaname]

He will have become stronger but no one can determine it. Do you think he could have beaten someone like Madara without his illness? I don't think so and it's not possible.

 

[Alien]

I assume that you think his potential is infinity.
I am sorry to disappoint you that Kishimoto himself said that, Itachi would never have won against Madara. He might have won against a Kage but that is where his skills end.