” Shikai: Despite not knowing its name his Zanpakutō is constantly released in some form of released state due to his immense Spiritual Pressure (much like Ichigo’s Zangetsu). In other words his Zanpakutō is constantly in a Shikai state without having the additional abilities a Shikai may grant its user.[80][81]. The sword’s appearance is a reflection of Kenpachi’s own practice of weakening himself to fight others on a even level: it is a chipped and seemingly worn-down blade with a guard that extends inward from its center similar to a shinai. The hilt is white although most of it is wrapped in bandages, as is his sword’s sheath. The blade is much longer than that of a standard Zanpakutō, roughly the size of a nodachi. Despite its appearance, it is easily capable of cutting through most objects. This is demonstrated when he stabs straight through Ichigo’s Zanpakutō and later slices a building in half with careless effort after releasing the full force of his spiritual power.
Shikai Special Ability: Unknown “

that’s why he can confirm which espada is the strongest

and your theory makes a lot of sense the strongest espadas dead before the weakest of them

The only two Espadas who have been proven to be Ranked incorrectly for sure are Ulquiorra and Halibel, and even then I shouldn’t say Ranked incorrectly, it’s just that Ulquiorra wasn’t Ranked based on his full Power.

Ulquiorra, who knows about his own Second Release, stated plain and clear that there are three Espadas more powerful than himself. Originally it was obviously thought that he was simply referring to Stark, Barragan, and Halibel. Then he brought out a Second Release which would make one think he jumped at least a Rank higher. So then that Statement was confusing. Then Yammy revealed himself to be the most powerful Espada and it all made sense. He was referring to Yammy, Stark, and Barragan. Ulquiorra’s Second Release did bring him up a Rank in terms of Power.

Some said “Well Ulquiorra was just saying that. He was obviously lying.”, which I personally believe is total and utter bullshit, saying that a Character lied to suit one’s own argument is absolutely ludicrous. As some one who agrees we have yet to see Aizen’s Army of Vasto Lordes not including Wonderweiss, you should understand where I am coming from, as I’m sure you like myself have come across those who said that Aizen was lying about the Vasto Lordes and when saying they were still maturing.

I have yet to see any proof that Ulquiorra is the most powerful Espada, let alone the most powerful Arrancar, that we have seen so far. There is nothing relative to compare his Power with. He went from owning Ichigo in his First Release to owning Ichigo in his Second Release. Therefore the most I would dare assume that his Power jumped up was merely one Rank. It’s highly likely that his Second Release was fairly new and therefore he wasn’t at his fullest potential with it. After all he did fail miserably with his Lance Attack and used up too much Reiatsu too fast it seems.

Going back to Yammy I think people need to chill out. First of all it’s obvious that the only way he loses any time soon is if Byakuya and Kenpachi both combine their Powers to beat him. Fighting is the same thing as Training, so I imagine Byakuya and Kenpachi are at least a little more powerful than they were when they fought Zommari and Nnoitra respectively. If I had to place my bets on where Byakuya Ranks in terms of Power, I most definitely believe he is more powerful than Halibel, and as for Kenpachi I would say he’s at least more powerful than Ulquiorra in his First Release. So their Powers combined should equal a lot more than People are giving them credit for.

I also think Kubo was trying to convey to us that he is obviously the most powerful Espada, by first of all making it a huge Plot Twist that he’s the Number Zero Espada, and secondly by having him refer to the rest of the Espadas that the Good Guys in Heuco Mundo had fought as weaklings compared to him. I know one might say that he was just bragging, and if that’s all that was said I could understand where they are coming from, but Ichigo acknowledged that it was true.

Therefore I am holding out on having my own opinionated conclusion on Yammy’s full Power until he is defeated. Until then though I’m sticking with him being the most powerful Espada.