User blog comment:CoolJazzman/Why do you think Yamamoto wasn't giving a promoted to become a royal guard./@comment-8295743-20130417035134/@comment-7658432-20130417091658

He wasn't able to defeat Aizen because Aizen took drastic countermeasures against him. He sealed his Zanpakuto, made him cover the flame blast he prepared. Heck, he defeated an Espada-class Arrancar (Wonderweiss) unarmed.

Now that's wrong, as of now, Kenpachi is the only one who defeated a Stern Ritter (correct me if I'm wrong) and we know Kenpachi has this monstrous strength and do not rely on Bankai. We know that these Quincy are so OP to the point that they can massacre Soul Society within a day.