It's not only his unique ability to split into (possibly) thousands of clones, thereby becoming nigh-omnipresent on multiple frontlines of a war.
No, but also once he had acquired the SO6P powers , he could use Truth Seeking Balls to defeat / vaporize literally 'anyone'.
Just like Naruto, he also inherited the powers of the 'Sage of the six paths'.
He's able to use powerful Jutsu like Amaterasu, which won't stop incinerating a target before it's defeated, but that's not all - Rinnegan also gives him access to all the 'broken' abilities Nagato used.
Even without his jutsu powers, Sasuke is still one of the most skilful melee / H2H- fighters, easily equal to Madara, and possibly not much worse than Might Guy.
In the far distant past , he also defeated Kaguya.
His skills in combat weren't displayed, so it's hard to tell how 'powerful' he really was. In any case - after transferring his powers to Naruto / Sasuke it makes sense that now Naruto & Sasuke are supposed to be 'at least' equal in power.
Regardless of how powerful she is, objectively, without the help of Black Zetsu she wouldn't even have come back into existence.
Her enormous chakra (power) is counterbalanced by her low battle intelligence.
At the peak of his power, when he had become the Jinjuriki of the Ten Tails, he appeared to be the 'most powerful' individual in Naruto - at that particular point in time.
However, he had had a ton of helpers before (especially Obito, Kabuto) which enabled his existence in the first place, so completing Tsukuyomi isn't exactly his 'individual' accomplishment only.
Also, due to the fact that Tsukuyomi had already been completed / cast on the moon at that time when Naruto & Sasuke had finally received their SO6P powers - we will never know for sure how well SO6P Naruto & SO6P Sasuke would have performed against Ten Tails Madara - under more 'neutral' battle conditions (without Tsukuyomi already being in place).
In any case, despite his enormous power, he still was far from being 100% invulnerable, and this was confirmed when Black Zetsu backstabbed him.
It's not only that he has the broken ability to teleport anything and anyone into the Kamui dimension, why he was so powerful and nigh-intangible.
It's also because once he had acquired the chakra of all the tailed beast , he became Juubito, and in this form (with Rinnegan & Truth Seeking Balls) he was hardly any weaker than Madara.
In his lifetime, he had managed to defeat Madara.
His cells were one of a kind, as they empowered him (and his descendants) with unparalleled self-regenerative abilites, as well as the ability to use powerful Wood Style jutsu.
Not only was he faster than light, but he could also teleport.
In emergency situations, he could also use the 'Dead Demon Consuming Seal' jutsu, which was strong enough to defeat the most powerful monsters, like the Nine-Tailed Fox.
By far the most powerful of the 9 tailed beasts, his tailed beast bomb could easily destroy mountains and a whole landscape.
Without Kurama's help, Naruto would've lost many battles.
Could control up to 6 puppets, and each single one of these six paths was already insanely powerful in their own right.
The Deva path could wipe out a whole village with little effort, or also use 'Planetary Devastation' Jutsu, and that's only one of countless Jutsu the Rinnegan (Six Paths Technique) granted to Nagato (Pain).
His very special Sharingan enabled him to use such advanced Jutsu like Amaterasu and Izanami - especially the later one is one of the most powerful Genjutsu of the whole series, just remember what it did to Kabuto.
He had one really good performance when he fought Madara & opened all of his 8 gates, and failed to defeat him only by a narrow margin. However, Madara wasn't trying to fight back too much, so this one fight shouldn't be overrated, either.
But ofc Might Guy had other good performances in fights before, too, e.g. against the strong Akatsuki member Kisame, so ranking him here, at #12, appears to be just & fair enough.
For this ranking, Kakashi was assumed to still have his Sharingan / ability to teleport objects & persons into the Kamui dimension.
This 'Kamui' jutsu alone is already 'broken' enough , add to this fact Kakashi's knowledge of thousands of Jutsu (the 'Copy-ninja') , his enormous experience & superior battle intelligence, and it's easy to understand why he deserved becoming Hokage, too.
I know there's lot of folks who believe Sakura isn't too powerful, but actually not only is she just as strong as Tsunade.
Remember when she fought Sasori in a cave and the walls of the cave were shaking from the sheer power behind Sakura's punches. So that's some amazing 'raw physical strength' which shouldn't go unrecognized for any 'objective' ranking.
Combine this strength of hers with her ultimate healing jutsu (creation rebirth - strength of a hundred: it heals any of Sakura's wounds quickly) , and you aren't gonna find too many characters that could defeat Sakura in a 1-vs-1 fight of 'raw strength', ever.
But ofc Sakura is not only physically strong.
Her knowledge of medical jutsu , her ability to summon healing snails which could heal hundreds of people simultanously, make her an invaluable asset for any team of fighters who hope to defeat an exceptionally powerful enemy.
If you consider he had little time to prepare / not enough knowledge about how Pain & his puppets worked together, it'S all the more amazing to see that he managed to defeat at least some of Pain's puppets. He was one of the legendary Sannin for a reason, that's for sure.
Said to have been even faster & physically stronger than the Fourth Raikage - however unlikely this may seem, once you've come to know the 4th.
As long he isn't sick, he sure is a force to be reckoned with, and approximately equal in power to Naruto in his (uncontrolled) Four-Tailed Kurama form.
He's also a brillant mind , knows a ton of jutsu (actually he prolonged his life for the primary purpose to learn them all), so for most battles Orochimaru can be expected to come tactically well-prepared , and with several trump cards (e.g. the bodies of deceased hokage which he could revive and use to fight for him).
His ability to handle multiple swords simulatanously is unparalleled.
Lives in perfect harmony with the 8-tails , so there shouldn't be too many enemies the duo of Gyuki & Killer Bee couldn't defeat.
Once he had mastered Sage Mode, he was strong enough to put up an surprisingly good fight against the Uchiha brothers (Itachi / Sasuke), although he lost, eventually.
He's not only a very skilful individual fighter, however, but also his high intelligence (knowing how to revive & control a whole army of Edo Tensei puppets) as well as his knowledge of healing jutsu make him a well-rounded , flexible and therefore powerful character.
With her paper clones, she can become nigh-intangible.
I don't see too many characters who would stand a chance in a fight against her, if they cannot even land hits on her.
So therefore I think Konan could easily wrap most opponents, who don't have exceptional powers themselves, into paper - and suffocate them.
She has all the strength & medical powers of Sakura and I only ranked her slightly lower, because despite of their similarities Sakura is much younger and therefore (probably) in slightly superior physical condition ('fitness').
Enormous physical strength & speed, which is almost unparalleled in the Shinobi world.
Can fly, and can also use a 'Particle style' jutsu that could potentially vaporize almost any opponent it manages to hit.
Not much is known, however, about how fast the projectile of the 'Particle style' jutsu travels, so chances are that most of the faster characters (which were ranked higher) might be able to dodge it / land a hit or some different jutsu on Onoki, first.
As long as he has Samehada and can drain the chakra & powers of his opponents, this powerful Water Jutsu user is very hard to defeat.
Because the longer the battle keeps going, the more chakra Samehada will have drained, and the more powerful Kisame's jutsu would become.
Anyone hoping to defeat Kisame should better end the fight as fast as they can, to limit 'Samehada''s broken effect of draining energy.
Can manipulate gigantic quantities of sand - a pessimistic estimate of me would be millions of tons - and crush pretty much any opponent beyond its weight.
At the same time, any attacks directed at Gaara which aren't exceptionally fast, are likely to be blocked by his sand shield.
Gaara's a truly powerful character & Kazekage.