I actually believe this, well strongest without the Otsutsuki family bs and disregarding the Juubi Jin's. Here's why:
Obito/Madara indirectly feared his potential, thus having him crippled:
The plan was to have Nagato use the Rinne Tensei to revive Madara after collecting the Bijuu.
Madara stated to use "his will" when using the Rikudou no Jutsu.
I believe that this imply's that when Nagato were to summon the Gedo Mazo Obito would have to use it and inject Nagato with "Madara's Will". When this was successful Nagato could be easily manipulated as he would not be healthy and in the right state of mind. While Nagato was not crippled he was still a threat to Obito. It was only after being crippled and injected with "Madara's will" that Obito could actually influence him and be near him safely.
As you can see here it was not actually the Summoning of the Gedo Mazo that crippled Nagato.
Here you can see that after the injection of "Madara's will" he gets malnourished.
Nagato no longer in the right state of mind because of "Madara's will".
After this, it was free game for Obito.
Nagato was also only a Teen when he became immobile and extremely malnourished. This would affect a lot of things. From his overall stamina, Chakra levels, how strong he is, etc. After he is immobile he couldn't train himself regularly like Shinobi do (physically). He countered this by using his Six Paths of Pein Jutsu. Even with these, he was splitting his Chakra by six (seven if his own body is counted) even if not directly, but he was constantly funnelling it when in battle. Because of the immobility he could never master the Rinnegan to it's fullest potential and he himself could not reach his prime.
Even brought back as an Edo, they are weaker than the "authentic" thing.
His Edo that got his youth back could take on Killer Bee, Naruto and Itachi at once. Although Edo Nagato got back his youth he did not reach his prime. All of the years of being immobile and not training his own body made his body weaker than another Shinobi in his/her prime. He never did "fully heal".
Taking all of this into account, the feats that Edo Nagato and Pein provided us, I have concluded that he could very well have been the strongest.
Nagato could multi-path.
His Edo was far above the paths which even overwhelmed Sage Mode Naruto.
His Chakra was not constantly split between six other vessels, he was arguably six times stronger, I'd say 5-5.5 times as Edo's are inferior if only slightly.
If he had not been cripple in his teen he still could have trained his body and Rinnegan to it's highest potential. His stamina, Chakra reserves would have increased immensely. He would not have to focus his Chakra on his paths when in battle, dividing it by six or seven if you include his actual body. There you have it
Thanks for reading!
Try not to hate too bad..
Obito/Madara indirectly feared his potential, thus having him crippled:
The plan was to have Nagato use the Rinne Tensei to revive Madara after collecting the Bijuu.
You must be registered for see images
Madara stated to use "his will" when using the Rikudou no Jutsu.
You must be registered for see images
I believe that this imply's that when Nagato were to summon the Gedo Mazo Obito would have to use it and inject Nagato with "Madara's Will". When this was successful Nagato could be easily manipulated as he would not be healthy and in the right state of mind. While Nagato was not crippled he was still a threat to Obito. It was only after being crippled and injected with "Madara's will" that Obito could actually influence him and be near him safely.
As you can see here it was not actually the Summoning of the Gedo Mazo that crippled Nagato.
You must be registered for see images
Here you can see that after the injection of "Madara's will" he gets malnourished.
You must be registered for see images
Nagato no longer in the right state of mind because of "Madara's will".
You must be registered for see images
Nagato was also only a Teen when he became immobile and extremely malnourished. This would affect a lot of things. From his overall stamina, Chakra levels, how strong he is, etc. After he is immobile he couldn't train himself regularly like Shinobi do (physically). He countered this by using his Six Paths of Pein Jutsu. Even with these, he was splitting his Chakra by six (seven if his own body is counted) even if not directly, but he was constantly funnelling it when in battle. Because of the immobility he could never master the Rinnegan to it's fullest potential and he himself could not reach his prime.
Even brought back as an Edo, they are weaker than the "authentic" thing.
You must be registered for see images
His Edo that got his youth back could take on Killer Bee, Naruto and Itachi at once. Although Edo Nagato got back his youth he did not reach his prime. All of the years of being immobile and not training his own body made his body weaker than another Shinobi in his/her prime. He never did "fully heal".
Taking all of this into account, the feats that Edo Nagato and Pein provided us, I have concluded that he could very well have been the strongest.
Nagato could multi-path.
You must be registered for see images
His Edo was far above the paths which even overwhelmed Sage Mode Naruto.
You must be registered for see images
If he had not been cripple in his teen he still could have trained his body and Rinnegan to it's highest potential. His stamina, Chakra reserves would have increased immensely. He would not have to focus his Chakra on his paths when in battle, dividing it by six or seven if you include his actual body. There you have it
Thanks for reading!
Try not to hate too bad..