Nearly anyone The powerscaling for Zoro is so ridiculous he literally blitzed Hybrid Kaido and deflected a combined Yonko attack. Let's break this down. Zoro 3 arcs ago wasn't even supposed to be stronger than Doflamingo.
Doflamingo was blitzed with no reaction by G4 Luffy. G4 Luffy got blitzed by a drunk Kaido in his base form. Zoro blitzed Hybrid Kaido not only blitzed but cut him as well and he still hasn't even mastered his haki.