Are you counting their ingame battle techniques or overall? Because if overall, you shouldn't use Saix's Berserk as a hindrance.
At any rate, I've heard that Nomura stated Xaldin was the strongest of the Organization other than Xemnas and Roxas. I've heard this from another forum member, so I am unsure if they were telling the truth or if the interview was legit.
If that interview wasn't real, then I would have to go with Saix. Aside from Xemnas, he pretends to have the least emotion out of everyone in the Organization overall. As stated in game, pretending to have emotions distracts them from their goals and makes them weaker. Saix was also 2nd in command, so I'd go with Saix.
EDIT: Now that I look at the poll, I see how underrated Lexaeus is. Keep in mind Lexaeus is one of, if not, the strongest Organization member in CoM. The only person that might be stronger than him is Marluxia. If anyone remembers the convorsation Zexion had with Axel, it basically emphasized Lexaeus' power and neither of them didn't seem to want to physically battle Riku due to his victory over Lexaeus.