Wait. Bee can continuously increase his speed through imputing chakra into Shunshin and slowly get faster and faster then he previously was simply because he has massive amounts of chakra? Since when has Shunshin worked like that again? Going by this, Sasori can move ridiculously fast because he has a lot of chakra containers and can constantly increase his Shunshin speed because of it. Going by this, we can say that Bee is well above Minato or Itachi - despite Itachi showing better bursts of speed, even against Bee - in terms of Shunshin speed because he can constantly increase his Shunshin through pumping chakra into it and because he has Bijuu level chakra that surpasses Itachi and Minato's chakra reserves quite a bit.
And going by this, Bee should be as fast as v2 Ay or hell, Kisame or rather Zetsu should have easily dodged or blitzed Ay or Bee because the former has Bijuu level chakra while the latter is a product of Gedo Mazou and is based off on Hashirama's cells, implying they have ridiculously massive amounts of chakra. Going by how you worded your statement, you are basically telling me that you can get faster Shunshin by continously pumping chakra into your Shunshin, implying Bijuu level characters would blitz the shit out of anything atm and you are telling me this would work in the same way as increasing the speed of the Iron Sand through stronger repellant force despite that I don't ever remember seeing or reading about Shunshin working in that way. Especially since it would then make no sense that Bee didn't blitz Minato - without FTG - or Itachi.
I don't see how he can match Sasori's raised speed of the Iron Sand and even outrun it in this scenario. Dodging? Have we ever seen Bee's dodging skills at Sakura's level, who was also backed up by an experienced puppet master helping her control her movements to dodge Sasori's attacks, especially when said puppet master stated she was familiar with Sasori's puppetry and has experience towering over both of theirs. Sakura managed to successfully dodge Iron Sand World that stretched out over the majority of the cave and left little to no room to move in, considered it branched off into multiple both big and small spikes.
Managing to dodge Sasuke's linear attack by moving outside his predicition capabilities isn't really impressive regardless of the fact that Sasuke is fast. Why? Because it was a linear attack and Bee had the matching speed. Nevermind the fact that Sakura and Chiyo dodged all of Sasori's needless so skillfully (well, Chiyo did, but that shows her ability to help Sakura's movements and familiarity with Sasori's puppetry) or that Sakura had trained in the department of evasiveness for quite some time, given that it was considered to be her specialty along with being a medic-nin and having a strong punch.
Lastly, Sasori can react in the same way as he did against Sakura and Chiyo. Just increase his field of effect and make evading impossible without getting a single scratch. Especially since we've seen Sasori stretch out or generate more Iron Sand than his puppet could actually carry inside of it, given it's height and width, implying Sasori can increase his amounts of Iron Sand quite a bit. Especially since the Iron Sand lake created after Iron Sand World fell down dwarfed Sasori who was standing on a stone sticking out of it.
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Among many other various cases of Iron Sand sudden expansion. Also, even with Sakura's and Chiyo's level of evasiveness, they were forced to put up shields in order to block Sasori's faster Iron Sand attacks simply because they were unable to dodge them. To finish off, Sasori is a sociopath who's shown some manipulative habits. A sociopath like him could trick/manipulate Bee into attacking recklessly.
This implies Bee's usual lariat actually works in a fully impactive way that would affect his whole body and make it scatter to pieces just like Sakura's direct punch to the center of his puppet body. As far as I know, lariat has only been able to rip apart the throat area atm. Doesn't actually affect the rest of your body through impact and Sasori's own body is hard enough to not get completey smashed by Sakura's punch. At best, he'll just send Sasori flying back like he did to Sasuke, assuming he killed him. Especially since he'd be assuming Sasori is a normal puppet master, thus assuming close combat and physical condition would be his weak link.
Now what happens when Sasori's body is scattered or flung back? Depends. Does he want to just make the pieces fly in the middle of the air and have it noisily click themselves back into place or does he want to just stealthily switch puppet bodies entirely, removing the need to fly it back into place? Third Kazekage puppet is a sufficient new body. Not that Sasori actually needs to put his body up again before attacking, considering the heart could control all the scattered puppet body pieces and fly them back into place through chakra strings. He can just fling one of the scattered blades into Bee's back after he turns around and done. Bee is poisoned, has a large blade piercing him and since he doesn't know about the heart, he can't react by smashing the heart.
Addressed the dodging thing above. As for the blitzing thing, countered by Sasori playing dead or flying up on Iron Sand.
He can punch through what with Raiton if it redirects his Raiton to another direction, leaving you with no Raiton to actually punch shit through with? Letting poison run through your body is not even a comparable scenario. Can you redirect poison from your body like steel does to electricity? Does steel have organs and functions like a living being to actually be affected by the process of letting lightning or poison stream through your ''body''? Redirecting Raiton is simple streaming through the Iron Sand into another direction.
And I don't really see how did you come to the conclusion that Iron Sand crumbles apart by being touched by Raiton. Gaara's normal sand never crumbled apart while being touched by Raiton. Did you perhaps mean that the Iron Sand would lose it's ability to stay magnetized, i.e. hardened through magnetism? Yes. But that simply returns the Iron Sand back into it's original state when Sasori took it out of the Kazekage, floating sand that works like Gaara's. It won't fall to the floor nor will Sasori stop being unable to actually use it as we've never seen him state that he can make the Iron Sand float through magnetism. Not particulary sure how you're supposed to make sand float with magnetism to begin with. He makes it float through normal chakra just like Gaara does with his sand. And if he wants it back into it's hardened state, he can keep on pumping magnetism into it.
Wait. How did we go from destroying Hiruko to leaving Sasori without Iron Sand by doing that? @Bold. Not really. At best he could assume it's another part of the puppet, not an actual organ that keeps Sasori alive. Neither Chiyo nor Sakura knew what that was until Sasori actually switched his puppet body and they saw that same piece of his old body was absent from his old body and was present in his new body, leading to a simple conclusion: it's what keeps him functioning. Otherwise, Sakura could have ended the fight by just rocking his heart in the first place when she pulled him.
He channeled Raiton into a sword. Different from shaping. As far as I know, Bee hasn't shown any Raiton other than his usual sword or palm streaming Raiton. Haven't particulary seen him shape and coat Raiton all over his whole arms.
Anyways, lets backtrack a bit. How exactly is this supposed to cut through the Iron Sand? Actually, let me be more specific. What type of Iron Sand? Defensive or offensive? Defensive? Sure. I'll give you that. He can cut through stationary, defensive Iron Sand, assuming Sasori doesn't suddenly transform it into spikes in order to stab Bee. Offensive? Not a chance. The layer around his arms or swords - referring to Raiton - is not only thin as all hell, but Bee cannot suddenly offer the opposing force hurled at him that comes with offensive Iron Sand spears, triangles, etc. Why? The weight of the Iron Sand would literally rip apart his whole arm - thus also poisoning him - before the Raiton could do it's job and mow through it. It doesn't have any protective properties nor does it erase Iron Sand's weight. As far as we've seen, the action of actually cutting through fat steel via Raiton
isn't instantenous. It never has been. Especially since Sasuke could provide a sufficient support to Suigetsu after Bee took his time trying to cut through Suigetsu's sword.
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So I'm not particulary sure what scenario you have in mind, but plowing through Iron Sand - spears, triangles, anything with an edge, etc. - with a simple layer of lightning that has no defensive properties and going against something that can easily tear through bedrock and has a spike that is clearly meant for piercing which is coupled with Iron Sand's weight will leave you without your whole hand as well as Sasori's poison. As for stationary defensive Iron Sand, ok. Ignoring that Sasori can spike it up or that it can redirect Raiton, it can plow through that.