UFC Champ Fabricio Werdum -- Floors Reporter with Vicious Leg Kick ... Wasn't Even Trying! (VIDEO)

UFC heavyweight champion Fabricio Werdum unleashed a featherweight version of a leg kick on an MMA reporter ... and it was still enough to send him to the ground in agony.

Aaron Tru has a history of allowing people to beat the hell out of him for no reason (check out the Ronda Rousey clip below) and this time he allowed Werdum -- who stands at 6'4" and weighs 232 pounds -- to kick him in the back of the leg.

It goes about how you would expect ... with Tru laid out in agony ... despite the fact Werdum claims he only used 40% of his strength.

Seems like he used 39% more than he needed to.