Who do you think would win?

Who do you think would win? A trained SAS solider who has killed men out in afghanistan with his own bare hands thanks to training taught by the army or an 18 year old kickboxer who has trained in kickboxing since the age of 5 and has won many many competitions in his country and is one the best and an expert in the martial arts? The kickboxer can also kick so fast that you can't see his leg move.