Not mine
I keep seeing people making claims about how prime itachi was 10x stronger than he was when fought sasuke, blah...blah. But I've got news for you guys, there's no such thing as prime itachi!
Remember back to what we saw with MS sasuke when he tried to activate stage 3 susanoo, he nearly went blindYou must be registered for see linksand that was his first time using it. What does this mean you might ask? it means that by the time your MS abilities reach their peak the effects of MS overuse will have already started to degrade your physical abilities. It should also be noted that sasuke stated that his cells where burning due to using just ribcage susanooYou must be registered for see links, sasuke was also coughing up bloodYou must be registered for see links. These are the exact same symptoms itachi's "illness".... it wasn't an illness at all, it was backlash from susanoo overuse! Just like sasuke, itachi had already undergone a drop in physical abilities due to cellular damage and blindness BEFORE HE MASTERED HIS MS!
now what does all this mean you might ask? It means that there was never a time when itachi had maximum physical abilities and vision along with maximum MS abilities. It's a trade off, the better his MS got the weaker his body became and back when he hadn't suffered any damage from MS his MS was untrained.
So I'll summarize by saying itachi was most likely at or very close to his prime when he fought sasuke. He traded away physical gain for more powerful eyes! and this isn't an insult people, like obito said he could have beaten sasuke easily if he had wanted to. But lets please stop conjuring up this make believe itachi who had no blindness and no cell damage but yet had perfect MS mastery b/c he didn't exist!
Discuss U_U