Conor McGregor told everyone that he was going to knock out Dustin Poirier in the first round at UFC 178. AND HE DID! McGregor caught Poirier with a questionable punch that landed behind the ear of Poirier, which stunned him, and then ended the fight with a flurry of punches. McGregor is one of the most popular fighters in the UFC, you can see why.
H/T as always to @internetican for the MMA GIFs