Was only really possible due to the secret behind it. He even said if Jiraiya had figured it out sooner then he would have defeated Pain. So if you go by that, then that means Jiraiya is the strongest, however if you go by that then that means the White Fang is the strongest, and if you go by that, then we know of a lot more strongest ninja's such as the Kage's (Most of them anyways).
But yeah my point is the strongest ninja would be Hashirama Senju
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My vote goes to Itachi and Nagato winning against Killer Bee and Naruto. But it would be a very great fight to see, definitely wouldn't be an easy one for any of them.
However if this fight were to happen, the show is called Naruto, so if anything Killer Bee would die but Naruto would find some way to kill both Itachi and Nagato and save the day.