Non of Itachi's abilities or victories are against the flow of logic established by the story's plot. You didn't name 1 example
Also, you just dislike the fact that Itachi pulled out Yata Mirror and Sword of Totsuka which is the only reason I am defending his place as one of the strongest shinobi's ever, legendary god items for the win. If I were you, I would prepare for Eternal Mangekyou Sharingan Sasuke, he is probably going to be just as sick, if not SICKER than Itachi

Now that he has Itachi's eyes, I wouldn't be surprised if he could summon double Susanoo, both his own and Itachi's and have the Yata Mirror and Totsuka Blade LOOOOL, what do yout hink about that

?