It happened again on Saturday night. Gennady Golovkin knocked out his challenger. It was his 18th straight knock out. And that is as amazing as it is a problem. In recent months, Golovkin has become like Mike Tyson at his height—the scariest man in the sport. The middleweight champion Golovkin has the biggest knock-out percentage (90.32 percent) of any middleweight titlist in history.