Ray Mercer boxed professionally from 1998-2008, was 36-7 in his career, and held the WBO heavyweight champion. He was formidable force in boxing’s heavyweight division.

For some reason Mercer decided he would give kickboxing and had a two-fight kickboxing stint in K-1, losing his debut to Musashi by unanimous decision. His second bout against Remy Bonjasky at the K-1 World GP 2005 in Seoul was even less successful, as you can see in the video.

Remy delivers what seems to be a fairly light head kick to Ray Mercer’s head. If you haven’t seen it, you’ll have to watch to find out what happens next.

Mercer also later tried his hand at mixed martial arts in 2007, fighting Kimbo Slice in an exhibition bout for Cage Fury Fighting in New Jersey, a fight he lost by guillotine submission. He did however find success is his other only ever MMA bout, knocking out former UFC heavyweight champion Tim Sylvia in 2009 by knockout :09 seconds into the fight.