Is itachi the strongest in naruto?

I wouldn't say he's the strongest, but he is pretty powerful. We don't clearly know when Itachi was healthy so we can't really say when he was at his full potential, but his Susano does make him pretty much invincible, but certain attacks are able to disable it. I would think that Nagato and Madara would be the top ninjas in Naruto. Madara knew a lot of info on Itachi so i'm sure he knew was to defeat Itachi.