Yonkō are the four strongest pirates in One Piece world. They were first mentioned by Vice Admiral Garp at the end of Enies Lobby. These four pirates’ powers are still unknown but after seeing the former Yonkō, Whitebeard in action and what he can do at his old age, I’m sure that a Yonkō can defeat any Admiral.
5. Ben Beckmann
Ben Beckmann is a member of the Red Hair Pirates and is their first mate. He was first introduced at the beginning of the series. His power level is still unknown, but we saw that his mere words were enough to stop Kizaru from attacking Law’s Ship. That means Kizaru’s life was in danger at that time.