X- yammeh- I've no reason to doubt he could overpower & kill released barry. raw power doesn't lie in teh Bleach & barry has taken damage from mid tiers- Hulk smash? Hulk smash! - Oscuras blast? Oscuras blast... -derp.
1- stark- defines the notion of 'primera' imo. the espada are a grouping of fighters that all show some clear inferiority to him in one way or another
2- Barry- because he has Arrogante!
3- Halibel- because she has the best close quarters priority & the most dominant ''sword'' imo
4- Ulqui- cuz we saw Noitra, Szayel & Wonderweiss regen too, then said to ourselves ''one of these skill bits is NOT like the other three'' and that ''one'' wasn't belonging to a Mr. Lou Cifer
5- Noitra- cuz he is clearly ''better'' than GrimJo
6- GrimJo- cuz he clearly has more mobility, utility & range than Zommari
7- Zommari- cuz his haxx clearly has more priority & convenience than Szayel
8- Szayel- cuz he is canonically a non-gillian tentacle monster
9- Aroneiro- cuz he is canonically a gillian blob monster
there is never any real reason to question Aizens rankings once you appraise the ''2nd release'' for the empty concept it is/or rather said- because lol at DC.
And then accept the ''Zero'' concept for what it actually is, spirit-energy/level stacking & zero being a value-less numeral representing change/potential. For in spite of any decent combat skill, yammis ''power'' is still given clear definition in his colossal mass post-res & his implemented preparation, as well as his ''variable state''(as noted by Yasutora) pre-res.
So I'm a reader & viewer that thinks the rankings are quite accurate or sensible when stuff like ''ability'' ''strength/power'' & ''skill'' are all factored in; heh, imagine that(its boring, I know...) I can even argue a case that each of the nine ''orthodox'' ranks were designed with inferiority to their immediate superior in mind if I merely sip the Kool-aid.