The rasenshuriken failed because of the armour [Lightning Release Armour.]
but after the 3rd raikage hits himself the armour is done for and that's the time when he's vulnerable.
Thought you'd know this much.
Further Minato was about to pierce 4th raikage who has his lightening shield with the Kunai
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and that same kunai has the capability to cut thr' 8-tails
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I think you raised a few valid points, people in this thread have raved and ranted about how Minato doesn't have a jutsu powerful enough to hurt the raikage, concluding that because of that, the raikage would winb the battle.
BUT! They fail to give us reasons for the raikage to achieve the victory, the same could be argued against the raikage based on speed, the raikage also doesn't have a jutsu FAST enough to hit Minato, so how will he achieve victory, he is a tad bit slower than A and Minato blitzes even A, so how would he hurt Minato?
Another issue is the one where everyone knows that Minato is the greatest seal master in the narutoverse and kushina said that he knew many seals and she ven tought him uzumaki seals, but if I said that Minatocould seal the raikage's chakra away with his seals, deactivating the armour, and then kill him, people would say I am speculating because we haven't seen Minato use that kind of seal, some of these people would be the same ones giving Kakashi wins in threads because of kamui even though we have never seen it kill anyone, or giving him wins because of copying one thousand jutsu even though we haven't seen him use these one thousand jutsu.
OR....they will say he won't be able to place a seal on the raikage during battle either because of speed or lack of ability to restrain the raikage, even though we saw Minato place a contract seal on tobi, who had intangibility and was fast enough to activate it before A could kill him when he tried to surprise blitz him.
And then I have seen people give Jiraiya a win against the third raikage because he can summon ma and pa, and ma and pa would supposedly trap the raikage with frog song so that Jiraiya can kill him, the same people forget that Minato was Jiraiya's apprentice and favorite student who was also a Kage and a TOAD SUMMONER, if Jiraiya would win by summoning ma and pa, why couldn't minato summon ma and pa too, he is a toad summoner after all.
And then the most vexing one, Minato would use reaper seal to seal raikage away, which would kill him too like it did against the kyubi, this shows exactly how misinformed people are. Minato only used reaper seal to weaken the kyubi by reaping away its yin chakra and taking it with him. To the death god's stomach, the kyubi sealed inside naruto was not sealed with the reaper seal, it was sealed with the four elements seal, he also used another four elements seal to seal himself and kushina into naruto, combining the two seals to form the eight trigrams seal. What is the point of me pointing this out, the point is, that we have absolute proof that the four elements seal can be used to seal not only bijuu like he did to naruto, but HUMANS as well, it even says so in narutopedia, that the four elements seal seals people/bijuu into items. if the raikage can't be killed, he can be sealed, WITHOUT dying like he would with the reaper seal.
Now back to your point, I saw that people were arguing with you that Minato's kunai wouldn't hurt the raikage BECAUSE of raiton armour, yet in the scene you posted it is quite clear that both Bee and A thought otherwise, B is A's tag team partner and brother, there is no way he wouldn't have known the limitations of the raiton armour, if he thought that the kunai wouldn't pierce the armour then he wouldn't have interfered, he would have just let Minato find out the hard way that his kunai wouldn't pierce, also, A thanked B for saving him after that incident, why would A thank B if he didn't think the kunai would pierce the armour? Why would he say B saved him? There is no way he didn't know that a kunai wouldn't penetrate his armour, its his jutsu, he would know about that, he didn't even expect a chidori to pierce his version 1 armour, why then did he think Minato's kunai would pierce version 2? And why did B think the same think, since he tried to stop Minato, then he obviously thought so. And how does a mere kunai cut through a tail of a bijuu? If mere kunai's could do that then no one would fear bijuu, clearly Minato's kunai had something special about it that both A and B noticed.
The only thing I can think of are three scenariors....
1) Minato has a wind affinity and tried to use wind frequences through his kunai to pierce A's armour, and used the same thing to cut through the eight tails. Reasons are that Kakashi told Naruto that Minato planned to add his nature affinity to the rasengan. Both kakashi and yamato said that a person becomes jounin in konoha when they learn to manipulate two affinties. Minato was a jounin. If we take Kakashi and Minato's words to be true, then Minato would have had two elemental affinities at his disposal, his son has wind, and the scene with him cutting a tail from the nine tails and almost penetrating A's armour can be taken as circumstantial proof that he also had wind. We have also seen raiton chakra cut a tail from the eight tails so far from sasuke and the third raikage, taking into consideration Kakashi and yamato's words, then Minato had two affinities too, and his fight with A and B suggest that he had one of them as a wind affinity, his son aslso has wind, and his name, namiKAZE can be used as not absolute, but circumstantial proof. Minato can penetrate the raikage's armour with his kunai or a wind jutsu, or at least disable the jutsu long enough to strike a killing blow with his spedd and transportation technique.
2) If it isn't the above then it has to be that Minato also has a lightning affinty, that is the only other possible way to do it, it would probably be his second affinity, pure speculation though, no evidence whatsoever for this except that it would be the only possible jutsu to penetrate the armour and his thunder related monker, like flying THUNDER god, the jutsui itself doesn't seem to have anything to do with lightning, but kishi rarely uses monikers that don't have some deeper meaning behind them, like for instance kisame's shark theme, guy looks like a shark and all his jutsu are shark based nature manipulation for example, but like I said, lightning element doesn't have much proof to back up either than speculation based on a lminimum amount of info, like jounin having two affinties and lightning being the only other possibilty to penetrate armour with a kunai.
3) Minato's kunai was made of a different metal and/or had something special about it besides the hirashin seal, maybe a penetration enhancing seal or something, there is no way a kunai alone can cut a tail of a bijuu right through, if it wasn't elemntal manipulation enhancing the kunai then definately there was somethig else done to it that made it have that kind of power and penetration, maybe a seal of some sort, he was a seal master of the greatest callibre afterall.
Some people said some silly stuff though, like the raikage crushing the kunai or ripping away the seal tags to stop hirashin, hell, minato doesn't even need kunai or seal tags, he can place a seal anywhere just by touching a place with his hand, all he has to dop is place seals around the battleground. Limiting is kunai arsenal is almost useless.
Would anyone figure out the secrete about the raikage's hell stab hurting himself without the info naruto received from dodai, Bee, and the eight tails, I highly doubt it, unless the raikage was stupid enough to brag about his jutsu, giving hints away in the process. But the raikage was paranoid about the incident with the eight tails and didn't even tell his own son about it, he wouldn't give anything away.
Even if Minato's amazing intellect aloud him the benefit of figuring it out, I don't think he could make the raikage hurt himself, Kabuto was the one controlling the raikage at the time and kabuto didn't know shit about the injury or the raikage's paranoia and embaraasment about the jutsu, but if the raikage fights Minato with his own mind and not kabuto's, then naruto's plan would never work, the guy was way too paranoid about the way he got injured and it was his greatest shame, he would notice the second someone even took a glance at his arm much less actually tried to target it, I think he would be too weary of a repeat performance. So I don't think naruto's plan would work even if minato tried it. The thirds armour and body were also stronger then A's so even if Minato can penetrate A's armour, it doesn't neccessarily mean he can penetrate the third's armour.
I don't know who would win here to be honest, it could go either way I think, Minato's seems too fast for the raikage but he seems too styrong and durable for him, it depends on the smarter one I think, we haven't seen the raikage fight when he is in control of himself so we don't know about his battle tactics and intelligence, Minato's incredibly smart and cunning though, I think Minato's sealing and barrier/space time jutsu would be the game breakers here if those dodnt work and his affinities don't work, then its a stalemate or he ends up losing eventually if the raikage is smart enough to find a way to get around minato's speed.
I give it a draw, to many what ifs and unknowns to make a clear choice.