Lyoto Machida is the most accomplished Karate fighter in MMA, in my mind. I say this because he has adopted Karate specific technique to cage fighting. There are a lot of fighters who have Karate backgrounds, but most opt for kickboxing and boxing type of techniques. With Machida, you see Shotokan Karate techniques. Sure, he is well versed in the popular fighting styles (boxing, wrestling, ju jitsu, thai boxing, etc.), but he brings something different that no other fighter in MMA shows. Some may criticize his methods (his patience and lack of aggressiveness), but he is one of the best.