Lol? Him being a perfect Jink does not make him immune to genjutsu. We already how Itachi put him in one during the war[
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]. The breaking process via the 8 tails is not instant.
In that duration he can easily get shitted on my amaterasu or better yet use Tysukuyomi to finish this. Don't compare Itachi to sasuke. They are two completely different people which means they both have different skill. Even during the DSM kabuto fight Itachi displayed better speed and reaction time feats. Not too mention he took Bee's 8 sword style attack like a cake walk[
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]. This goes back to show in part 1 Lee saids if the body cannot keep up then the sharigan prog is useless. Itachi took down 3 grown men with matured 3Tomeo instantly[
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].