Hancock if ace isn't as idiotic as luffy ace may win if he is but Hancock still has strong as Haki and her kick was able to severely damage a pacifista with one blow
This is all DF. Her ability petrified the Pacifista metal into stone that she broke with her kick. It just shows Hancock can break stone... Something Arlong Park Sanji can do.
Ace is a ranged fighter and shares Luffy's persona. He's not getting Mello'd.
Hancock's rage fueled kick on Smoker hardly hurt him. She doesn't have strong Haki feats... No nearly as strong as Blackbeard.
If we went souly in feats I'd plausibly say Ace since he can gain the distance advantage, possible flight advantage, and definite damage/destruction advantage.
But if Hancock gets in close...she probably wins with her petrification ability.