LAS VEGAS – When the meaty palm of Vasil Kamotskii, a 360-pound, 34-year-old pig farmer from Siberia known as Dumpling, struck the tender cheek of the man who faced him, it sounded like a thunderclap. Dumpling didn’t appear to expend much effort – he swung lazily, the way you might bat a fly. But it was enough to send his opponent, Kamil Marusarz, a 26-year-old from Orland Park, Illinois, toppling to the ground.