I've heard a lot of contradictions concerned with such question. The one side says it's ok if you want to fight and Allah approves it when another side disagrees. How this sport can be approved by Allah if fighters are half naked fighting for glory or belt and not for his sake and justice? It's right to compete in the sport where people break bones ( get injuries, head trauma and so on so forth) to each other for getting money prizes or glory? Hope to receive the certain and complete answer.