Hey, Dr. Proof. Sasori might be easier to convince you otherwise, since his weakness to Itachi is subtle, but pure:
- Itachi can immediately see the heart cannister due to chakra vision.
- Sakura was able to evade Sasori's attacks after decoding his finger patterns.
- Itachi, with his superior intellect and Sharingan, would immediately decode the patterns.
- Sasori stated a puppet-user's weakness is ninja getting in close range and attacking them.
- Itachi's flicker and feints are easily among the fastest in the manga, shocking many top tiers.
- Once up close, the heart canister could be easily gripped with partial Susano'o, which is ridiculously fast.
- For example, even someone as fast as Edo Itachi could not evade Sasuke's partial Susano'o on speed alone.
Basically, Itachi makes Sakura and Chiyo look like pushovers. Even without his Mangekyō, so long that Itachi isn't sick, his ridiculous speed and reflexes, combined with his dōjutsu insight into Sasori's weakness, would make him a very dangerous foe. He will definitely manage to get up close, either with a flicker burst that shocked Bee or a feint that twice shocked Kabuto, and then grab and crush the cannister with his aragami extension.
The popular opinion that Sasori is immune to genjutsu isn't necessarily valid either, as genjutsu works on entities without brains, such as tailed beasts, which are actually pure and sentient incarnations of chakra. However they sense the world, Sasori uses a similar system, and both systems are vulnerable to genjutsu. Kakuzu being affected falls under a similar pretense, although there's nothing to suggest that Kakuzu doesn't have a brain, so it's unnecessary.
Edit:
As for Kakuzu, a broader approach is required, so I'd like to reinforce a few points. The first is simple, and that is to reinforce how ridiculously skilled
base Itachi is as a ninja. He is one of the only ninja that has blitzed Sharingan users, and he danced around Naruto and Killer Bee's simultaneous taijutsu attacks. Itachi
is capable of evading the hearts without the protection of Susano'o, and the hearts aren't so durable that his fire jutsu and large shuriken wouldn't suffice in destroying them. But the real topic is if and when Itachi becomes deadly serious:
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As you can see, it's quite large when Itachi uses his final form, much larger than any form Sasuke has shown. And more than that, Itachi's Susano'o is
fast with the Totsuka. In its first showing, it decapitated seven striking serpents with multiple slashes (covering several hundred meters of distance each) in such quick succession
that all the heads hits the ground simultaneously. Moeover, both Nagato and Orochimaru were unable to register the Totsuka's thrusting speed until they had already been pierced. And finally, recall that Uchiha Madara's conscience and the databook refer to Itachi's Susano'o as being the paragon of both offensive and defensive ninjutsu because of those items. It's out of Kakuzu's league.
