It could have been Zoro given he got such an Op PU, bt he already showed his desires to cut Orochii, and he got Enma sword to being to cut the mysterious Snake Zoan.
So it could be Law, he is lot stronger than Zoro, also has Hax df, won't faint and can appear behind flying King Zoan with instant Shambles and so can easily deal with King.
Bt Law also has to deal with Kaidou, so maybe Oda might throw Zoro two bones this arc. Ofcrs King can be nerfed as much as Oda wants for to make Zoro win possible. And Killer can also help.