*Cracks Knuckles* Let's begin.
To start I just want to say that I believe that Sasori and Itachi are very evenly matched and that Sasori is immensely strong, but for the sake of being a devils advocate I will choose to defend Itachi's position.
Sasori's main fighting style is long-range and he hopes to overwhelm you with his techniques, whether that be 100 puppets or iron sand etc, that's the main goal. On the other side Itachi seems to be a mid to short-range fighter who uses feints etc to draw his opponent off-guard and then defeat him that way (he is an innate pacifist). Now this is not to say that either one can not switch up fighting styles, it's just their preferred. As Kage tier shinobi they can adjust to the situation.
It seems that your main points as to why Sasori could beat Itachi is his use of the 3rd Kazekage and his iron sand/magnet release and his 100 puppets with poisoned weapons. Also a major part of Itachi's arsenal is apparently useless because Sasori cannot be affected by genjutsu. That is all well and good
except:
Iron Sand/Magnet Release:
This is pretty much useless against Itachi and here's why; Itachi is a fire style user. He hails from the Uchiha clan who is naturally proficient at fire techniques and he was regarded as one of the best in the clan ever. (Sasuke could create the Great Fireball at age 5 but his father said Itachi was much better etc etc) Itachi would not struggle with using fire techniques throughout the whole fight because of this. Why is this important? Because, fire is what would demagnetize all of the kazekage's manipulation. We know that his techniques are a nice bright orange color, this equates to a temperature of roughly 1,100C. Iron loses its magnetic properties at 770C. So essentially anything that involves Magnetism/Magnetic release/Iron sand is irrelevant. Itachi does not even need to resort to Amaterasu because Great Fireball and Phoenix Sage Flower Nail Crimson are more than sufficient (and his stamina/chakra level does not really come into play yet because he is so proficient at fire release and is not using his mangekyo).
Puppet techniques/Poison:
I believe that Itachi's intelligence, ability to use high level water and fire techniques and the use of his crow and shadow clones would be able to dodge and escape Sasori's mass attacks. BUT even if that is not enough, Itachi could resort to using Amaterasu to destroy most of the puppets/block their attacks or even go so far as to activate Susanoo and protect himself that way, as I don't think the puppet forces are enough to penetrate Susanoo.
Sasori being unaffected by Genjutsu:
Now this is obviously debatable but here are some reasons why Sasori COULD be affected by genjutsu, thus ending the fight even quicker through the use of Tsukuyomi or Izanami. **I fully acknowledge that he could not have a brain etc etc. Sasori is a HUMAN puppet and a being in the naruto universe. In order to fight you Have to have the senses working in order to see, hear, feel, etc. There has to be some kind of input and processing unit that allows him to live breath and fight. Thus, the there has to be some kind of chakra network that could be disrupted. Let's say that he doesn't have real eyes so he can't be put under by ocular jutsu, Itachi could still trap him in Izanami (which affects the five senses, and affected Kabuto despite his attempts to not be affected by the sharingan) so he could force him to lose the fight that way. This might be seen as a cop out win for Itachi, but even without this Itachi could still beat Sasori.
And lastly, another way that Itachi could defeat Sasori is by finally using Susanno and utilizing the Sword of Totsuka (which is an ethereal sword) to extend the long distance that could seperate them and seal Sasori in the "genjutsu-like 'world of drunken dreams' for all eternity" like what happened to Orochimaru and Nagato. If Itachi were to resort to using the three Mangekyo powers then it is hardly possible to see how Sasori could win. His intelligence, speed, array of jutsu and over all prowess gives him the win in this 1v1 battle.
This is a fantastic thread and depicts both Sasori and Itachi very well and shows why Sasori should not be underrated by any means, but to be honest Itachi is just a bad match-up for Sasori. Props Negative Knight and Co. Keep up the good work
