I'm voting Zoro due to his absurd skills and analytical prediction, ability to probably sense Akame for King's reasons above, and ability to boost his stats past the 2x AP Gap (via Haki, Enma, Muscle Expansion, Hao Infusion, Goken, and Asura).
Goken and Asura especially, since the former has consistently with just 1-sword used beaten people who a normal 3-sword Zoro couldn't beat (not to mention in Enies Lobby Goken matched a Double Rankyaku from Kaku, which is double one Rankyaku which matched normal 3-sword Zoro), and Asura is a 3-times multiplier so even a 3x multiplier of base Zoro (who is 760 teratons via backscaling from Base King) would be 2.28 petatons, and Buso Asura (which is 3x normal Buso Zoro, who matched Base and Zoan King who is 1.032 petatons) would be 3.096 petatons, or nearly double Akame's AP/dura of 1.58 petatons.