This is video of a mixed martial arts bout in Brazil between Evilasio Silva and Claudinei Angelo in which Angelo quits during the fight, jumps the cage, and then just walks away.
This is video of an mixed martial arts fighter who breaks his leg after delivering a kick to the leg of his opponent. The video is graphic, so don't watch if you're squeamish.
This is video of 62-year-old Wayne "Kung Fu" Smallwood knocking out out his opponent in a little over one minute, to win a recent mixed-martial-arts fight.
Spinning back fists is an important part of every great fighter's arsenal. Make sure you know how to do properly perform the move before attempting it in a fight. Otherwise, this happens. Ouch!