You're screaming at air now. What are even trying to say? Kuzan was talking about Mingo's influence. Why so obsessed with power level?
Kuzan was talking about everything that makes Doffy who he is, his connections, his individual strength, his influence, his personality, his military might, his potential lineage, his rule, his clothing choice, his coc. Everything.
The characters in the verse aren't judging Doffy based off his performance in a boxing bout, strength is so much more than that in this verse, and Doflamingo is a big shot. So again, his arrogance in the scene in the OP is well earned as Kuzan later lets us know. He's arrogant, but for good reason. He is an exceptionally rare class of pirate. And yes even individual strength has to be adequate here, Doflamingo is already one of the few chosen by the heavens (CoC), that alone distinguishes him, but then there's so much more that he was able to do in his career which makes him extremely dangerous to deal with.