Do you think that tsunade can beat Itachi if Itachi will not use susanoo? that means that itachi does not have a defense, what allows tsunade to kill him with one punch. tsunade can also regenerate herself from any damage that itachi can make, even if amaterasu will hit her. he easily tanked madaras katon techniques. genjutsus are also not as much effective against her as against others. she is a healer and healed kakashi from tsukuyomi, she is a senju and we know that the senju were at least on pair with uchihas and hashirama senju beat madara.and tsunde possesses hashiramas will as she said what is more important than any strength. the will which allows her to break even genjutsu.