8. Roy Nelson vs. Big Nog (Antônio Rodrigo Nogueira)
Event: UFC Fight Night 39 - April 2014 The only reason this walk-off knockout isn't higher on the list is that it was actually painful to watch. Big Nog is a legend. The Brazilian Jiu-jitsu ace has been champion in Pride and the UFC. He's one of the greatest heavyweight mixed martial artists of all time. However at 38 and with many wars behind him, he's lost a step. Several. Against Nelson, he continued to shamble forwards like a zombie despite being continually tagged by Big Country. He would not go down easy, and though he tried to lure Big Country into his guard, Nelson, a BJJ black belt himself, was wise enough not to engage with the more experienced ground fighter, and bided his time. Sure enough, Nogueira circled into a Nelson right hand. He hit the canvass, stiff as a board. He hit hard. Nelson didn't even try to follow up, just simply walked off, knowing he had ended Big Nog's night - and possibly his career. Nogueira does want to fight again, but the question of whether he should be allowed to is the elephant in the room.