Owens I think takes the cake but what happened on July 4, 1910, at Reno, Nevada, is right up there.
Jack Johnson defended his heavyweight title against Jim Jeffries, who had been goaded out of retirement to try and retake the title for the white race. There was such tension before the fight that the promoters banned guns and also anything that could be thrown hard, including apples, from the arena, which was a big deal in the West 114 years ago. The crowd was intensely hostile towards Johnson. Johnson's victory triggered race riots that evening in more than 25 states and 50 cities. At least 20 people were killed and hundreds more were injured.
I cannot think of another more violent lead-up and outcome to a sporting event.