A video has just surfaced showing a man purported to be Kanye West fist fighting like a champion ... knocking 2 guys out cold. If it's Kanye it could be disastrous in his upcoming criminal case because prosecutors want to show he's violent by nature -- HOWEVER TMZ has confirmed ... the fighter is NOT Kanye. The video was shot in Austin, TX and Mr. Kardashian wasn't there at the time this hit the Internet.