Re: Can Tsunade take on Itachi or Kisame?
To the "or Kisame"-part. Depends where, and whether Kisame has shamehada. After all Tsunades punches is greatly weakened under water, and suffocating - well it will kill the cells, if they get no oxygen, so her regeneration ability wont work.
Regarding Itachi.. Well Tsunade can't touch Itachi without being hit by amaterasu, if he uses it as a shield. How does Tsunade get close to Itachi anyway, when he uses suanoo, amaterasu, etc?
And no.. Tsukuyomi can't be broken by Katsuyu, wtf are you thinking..... It's a genjutsu that lasts 1-3 seconds in real life, and it feels like 3 days. Even if katsuyu sees it quick to break it in 1-2 secs (which she by most chance wont), tsunade will still take a huge deal of damage, and itachi using amaterasu right after.. she wont dodge it. But depends whether itachi actually can use amaterasu, since he also takes damage from tsukuyomi for a bit. Of course she will just have to avoid eye contact then, but goes back to my initial question: how does tsunade hit Itachi?
In fact you are underestimating the sharingan so much, it's a sad disgrace to the manga. Itachi can beat Tsunade with tajutsu... She will never hit him. He can see through every single attack she uses, and he can take her down with shurinken (since he is above anyone at that), and though tsunade can just regenerate afterwards, it still gives her no way of hitting itachi. So tsunade can't even outlast itachi in means of chakra. She stands no chance.