Board Thread:Questions and Answers/@comment-24847491-20141024100731/@comment-24769684-20160531210346

Pulled this list out of my ass, but here's my basic idea. Keep in mind that even the captains at the bottom of the list are still extremely powerful. I'm also including the Royal Guard.
 * 1) Ichibe - leader of the most powerful faction of Shinigami, has the ability to erase one's entire existence
 * 2) Nimaiya - arguably Soul Society's greatest swordsman, dispatched Yhwach's four most powerful soldiers in seconds without using Shikai or Bankai
 * 3) Yamamoto - Most powerful Shinigami in the Gotei 13, can annihilate anyone near him with his Zanpakuto, also extremely skilled at hand-to-hand combat, both Aizen and Yhwach had to use living dummies to absorb his power before they could do anything.
 * 4) Senjumaru
 * 5) Hikifune
 * 6) Tenjiro
 * 7) Aizen - A genius with sheer raw power to back him up, has an extremely broken Shikai and never had to use Bankai, extremely proficient in Kido
 * 8) Shunsui - Next in line to be Captain Commander, master in both swordsmanship and Kido, has extremely powerful Shikai and Bankai, took out the top Espada with just Shikai, and managed to damage an intangible warrior
 * 9) Urahara - The smartest captain; his Shikai and Bankai have many possible uses; is always 900 steps ahead of his opponents
 * 10) Kenpachi - The day he unlocks the entirety of his power he will probably either join the Royal Guard or get killed by Central 46. Guy is simply a monster, taking down Espada and Sternritter with his unreleased blade and being able to annihilate both imagination and miracles with his Shikai and Bankai. I'd say that at this point, he's surpassed Unohana as the true Kenpachi
 * 11) Unohana - the previous Kenpachi, a crazy powerful warrior who can also put on a great act as a docile healing captain
 * 12) Ukitake - possibly Shunsui's equal in terms of combat prowess, but is a bit below him due to his sickness
 * 13) Mayuri - Not as smart as Urahara or Aizen, but still a genius. His already potent Zanpakuto is made even more powerful by his modifications, and he will go to any length to stay a step ahead of the competition. Went toe-to-toe with an Espada by himself for several chapters before his own creation dealt the finishing blow; it's a win for him, even if he didn't intend it to happen.
 * 14) Byakuya - Guy has always been set up as powerful, despite his rather simple power he has managed to stay interesting and innovative even as Ichigo and later villains reached his level. Also a master of both swordsmanship and Kido
 * 15) Hitsugaya - Second to Kenpachi in terms of untapped potential, Hitsugaya has already reached great heights in his young age and will likely surpass many by the end.
 * 16) Yoruichi - Master of Hakuda; she is notable for only placing emphasis on that single method of battle while mostly ignoring her Zanpakuto. This helps allow her to gain true mastery of a skill instead of juggling multiple, although she falls short of many captains who have successfully mastered multiple skills.
 * Gin
 * 1) Soi Fon
 * 2) Shinji
 * 3) Rose
 * 4) Kensei
 * 5) Love
 * 6) Tosen - With control over four of the five senses, Tosen's power should be vast. However, Tosen's fatal flaw is that he cannot consider his power's weaknesses, and is too easily distracted by his ego.
 * 7) Komamura - Guy is mostly all about one-note brute strength. And when that strength is unable to take down an opponent, Komamuri is pretty much at a loss.
 * 8) Isshin