Doesn't Itachi kno the forbidden techniques izanimi(I think thats what its called) and izanagi. Itachi wins even without those sorry sasuke.
Izanami is almost impossible to use against the level of opponent he'd need it for, and Izanagi will only save Itachi's life one time and leave him without two MS jutsus.
I dont see Sasuke winning this..not that he wont its just that I cannot see it.
Itachi has an invincible susanoo and from we have seen Sasuke does not. When it comes down to susanoo vs susanoo...Itachi wins. Itachi can also manipulate time in his genjutsu and not to mention is intelligence is above Sasuke's as well. So is his battle experience. His intelligence is clearly superior (not saying sasuke isnt smart). Itachi was said to think like a hokage at age 7. He mastered the sharingan at age 8, was captain of anbu at 13 and soon annilated his entire clan around that age. Sasuke was unable to master that sharingan until at least 13 (around when Itachi was able to kill the entire clan) not to mention the villlage heads trusted a boy to carry out such an impossible mission. This is proof Itachi was exceptionally gifted in intelligence. Combine that with a superior susanoo and genjutsu there is no way Sasuke could kill a healthy Itachi with the intent to kill. Or at least from what we've seen he cannot.
Itachi wins with 4-5 difficulty
Itachi's Susanoo isn't invincible.
Itachi thinking like a Hokage just means that he was concerned about the village and it's people when the other kids were playing around.
Mastery of the Sharingan does not display one's capability: Obito became a Chuunin without a Sharingan, something Itachi can't attest to. Madara was also taking out elite Senju ninjas without a Sharingan at a young age, Itachi can't attest to that either.
Itachi didn't attack his clan head-on, he ambushed them by surprise, especially since he was the last one any of them expected to attack them. He also needed Tobi's help, he couldn't had done it alone. Old Hiruzen and Danzo without mods were capable of taking out the Uchiha head-on.
Healthy Itachi does not exist in the context that you're using, and is just pure fanfiction anyway.
Amaterasu/Tsukiyomi degrades the eyes, Susanoo degrades the body. The effects are permanent and only reversible by EMS.
And yes, Susanoo degenerates the body. Sasuke was using a partial Susanoo and was complaining about how every cell in his body hurt, he was staggering, and he was coughing up blood; he also wondered what it was like for Itachi whom had mastered Susanoo. The databook also said that Susanoo drains the user's life away, that's the cost of using it. So "Healthy Itachi" is either Itachi without MS, or he's still a novice with MS.
Now people may hate on me but let me elaborate here...
I do believe it would be a VERY close fight but! Itachi wins in my book mainly do to a few factors.
1. Itachi is more experienced in Taijutsu than Sasuke giving him the upper hand when things get close and personal
2. I think that Itachi is proficient enough with Genjutsu, that he would either use a jutsu Sasuke can't escape from like Izanami or he could even keep Sasuke in Tsukyomi if he WANTED to regardless of his Sharningan or EMS.
3. Itachi is vastly more intelligent and tactical than Sasuke and can analyze things and make quick decisions on his feet way more efficiently.
4. If this a battle at maximum potential and skill meaning Itachi is healthy, not blind and not sentimental, then again this gives him the upper hand.
5.One stab from the Totsuka blade and Sasuke is done, also the Yata Mirror is impervious to everything which overall means Itachi has a stronger Susanoo than Sasuke does, and is more experienced with it.
2. Itachi hasn't shown the ability to do that, Sasuke has also broken Tsukiyomi. And Sasuke has been hit by it full-force twice before and never noted that it was any weaker the third time.
3. "Vastly"? I don't see how.
4. "Healthy Itachi" cannot and does not exist, he's fanfiction. Read what I said above.
5. One stab from any sword and it's done, Totsuka isn't special... it also has to actually hit Sasuke. Yata can only block in one direction, so if Sasuke can set up a feint he could get past it. Sasuke could also try to wrest Totsuka and Yata from Itachi's Susanoo, they aren't connected to it. Yata also has a potential weakness, the databook implied that it only stops one attack at a time, so Sasuke could launch two different attacks.
