Like i've said, he won't dodge her attacks for too long and he will run out of stamina. I'm not saying he can't dodge her attacks, but i'm saying that during the fight he will slow down and get killed if the fight last long like against Sasuke where he was really on his fit at the begin of the fight, but was almost dead in the middle of it, incapable to dodge some attacks that he usually can. His stamina is the real problem here. He can't dodge her attacks for too long. And like i've said, he has no killing moves to beat her, and we're talking about Tsunade who is pretty immortal. Genjutsus? We've seen that with regular sharingan genjutsus, if you hurt yourself you could counter it(Kurenai did it, Orochimaru too), so regular genjutsus won't be a problem for Tsunade. She will hurt herself. Also in the case you say it won't work, just don't forget we're talking about the woman who healed even psychological effects from Tsukiyomi. That means she is mentally capable to withstand such things. And if you still don't get it, don't also forget Tsunade has summons. She could summon Katsuyu and put her on his back. It will help her to go through regular sharingan genjutsus.
Genjutsu is not really a problem. Itachi could use it as a feint, but to do what after that? Like i've said, he has no killing moves. And Tsunade will only be there to regenerate. Tsunade is not idiot too to do the same mistake twice. She must know Itachis genjutsu power and she will be prepared for that.