@The:
I think Yamas main merit is shutting up absolutely retardedly overconfident characters, because man this OVAHKILL Quincy is the most optimistic guy ever.
"What, you think you can beat me, Yamamoto?"
"Yeah!"
"Using a stolen bankai you don't have complete mastery over, and doesn't constitute your main fighting style?"
"Yeah!"
"Using a bankai from my subordinate, a vice captain?"
"Yeah!"
"Vice captains being amazingly inferior to their captains in terms of strength?"
"Yeah!"
"Even though the bankai in question is Sasakibes?"
"Yeah!"
"And I'm the friggin Captain Commander?"
"Yeah! the way you're making no effort to dodge my attacks and don't seem to be affected at all is a GREAT sign in my favor, don't you think?"
…
Disentegration
You'd think the Quinzis would actually have some sort of strategy for taking down Yama; like getting him to kill all the other shinigami through his sacrificial ultimate flameout move