Prep during the battle.. Sasori is unaffected by Hanzo's poison,
Incorrect, so much as a scratch from Hanzo's poisoned blade would render Sasori poisoned if it actually hits Sasori (his core). Its kind of a mute point when arguing Sasori and being poisoned. The thread is about the best poison User. Not the best at countering poison. Heck if you go that way, Sasori is basically immune to his own poison. The only way to injure and kill the dude is hitting his organic core case that's usually in the heart of his puppets. Besides, hitting it is a kill as it is.
So y did this not happen against the Sannin.. Or immediately with Mifune when they fought in their earlier days..I rest my case
Both fights showed Hanzo wearing his mask. His Toxin was so lethal, that if his Salamander sac were to be ruptured in battle, even he would be stunned. Thus, he wears the mask to protect that from happening. You see, in a warzone, it isn't just One on One. He has to think about after he defeats his foe. Getting stunned in that type of combat is instant death.
However, in a 1V1 that has no repurcussions, he'd easily be capable of fighting with his mask off.
1. Hanzo
2. Sasori
3. Orochimaru
4. Torune
5. Shizune
6. Kankuro
7. Kidomaru
8. Akon and Sakon
9. Sakura
10. Anko
Sorry, however, Tsunade has NEVER shown the use of poison in combat. She's only shown to be capable of teaching Sakura how to handle it for antidotes and medicinal purposes.