I would say Chidori. Everybody and they mama knows Rasengan. Minato, Jiraiya, Naruto, Kakashi, Boruto, even Konohamaru...it's the modern Kamehameha, where you have fodder (Konohamaru) learning the technique.
Chidori
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Rasengan
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You know that nearly everyone can learn it, beause it does not take an impact from your nature transformation - chidori, on the other hand, takes. You need to have lightning release to create one.
That does not mean that rasengan is easier to master.
Even so given the speed and reflexes you need to master the chidori and the fact that it requires hand seals makes it more difficult to master imo. A fodder was able to use rasengan, you don't see fodder walking around with Chidori in their hands lmao
Even so given the speed and reflexes you need to master the chidori and the fact that it requires hand seals makes it more difficult to master imo. A fodder was able to use rasengan, you don't see fodder walking around with Chidori in their hands lmao
Chidori is like rasengan with lightning more or less. I've seen 3 people use that
However I've seen absolutely nobody else use rasenshuriken which is a rasengan with wind element
it's a straw argument trying to connect the number of users a jutsu has with it being harder to master. Sasuke is the only person that tech got handed down to so of course it would have less users than Rasengan, especially because Konohamaru possessed tools to help learn it faster and easier. That doesn't mean he's mastered it. Naruto didn't even master Rasengan until he created the RS.i would say chidori hope that doesn't make me a troll kaira and kesonfire
based on how konohamru used rasengan while being a genin. that to me kinda made the jutsu really basic
and the only people to use chidori are sasuke and kakashi