Septimus Prime
Member
I don't think he really has morals; he just pretends to, but he plays his cards very close to the chest.Uraha is probably limited thanks to pesky morals. Mayuri has nothing of this shit and probably better budget and equipment to research than Uraha.
Either way, I think that even when he holds back, he's way more powerful.
The guys who've barely done anything are the strongest, I'm sure. Remember when Isshin showed up in the last arc and threw Aizen across the city by just flicking his finger? Urahara is in that class of badass, I think--along with Kyoraku, Ishida Sr., and the current Aizen.