Susanoo consumes the user's life and affects their eyesight and body. It is said that Susanoo's defensive abilities are not absolute. It doesn't protect the feet, can be damaged during its development stages as well as being separated from the user. It is also possible to bind Susanoo's movements and restrict his mobility [
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] I think Sasori's Iron Sand attacks such as Iron Sand Gathering Assaults and World Order can prevent Itachi from achieving Susanoo's complete form. If Itachi can breathe inside Susanoo, it means that the air can pass through. In that case, Sasori's poison gaz should be able to have effect and poison Itachi.
The sword of Totsuka seals everything it pierces into the gourd held by Susanoo. If Sasori manages to dodge the sword, I don't think it will cause too much trouble. I agree that it's a dangerous weapon and has to be avoided at all cost.
The Yata Mirror can "change its own characteristics depending on the characteristics of the attack it receives, making the technique ineffective." If Sasori hits a spot which isn't covered by the shield, the protection granted by it will be ineffective. I am not saying that it will necessarily break through Susanoo.
Sasori isn't affected by genjutsu because he doesn't have a brain. All of Itachi's illusionary techniques are rendered useless.
Sasori has 5/5 for stamina when Itachi has 2.5/5. Since Susanoo uses a lot of chakra, Itachi will be exhausted. No matter how skilled Itachi is, there is no guarantee that he will be able to dodge every iron sand attacks even with Sharingan prediction and to have nothing, not even a single scratch. [
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] A small quantity of poison is needed to cause paralysis. Since Itachi doesn't have antidotes, his body will go numb and he will die in a few days if not treated. There are some attacks that cannot be dodged such as Satetsu Shigure. Chiyo and Sakura didn't even try to avoid the iron bullets because they know it couldn't be done. That's why Chiyo used the chakra shield installed in her puppets. Itachi doesn't have knowledge about the Sandaime Kazekage and the techniques he can use. The moment Sasori finishes preparing the attack, evasion becomes nearly impossible. It’s if Itachi is out of Susanoo. Satetsu Kesshu and Satetsu Kaihou can both cause problems to Itachi.