He's alright. My main problem with him is that he falls into the same annoying area that a lot of non-powered characters with martial arts training do, where just through training he basically has super powers akin to Spider-Man's and is pretty much perfect and unbeatable. Its unrealistic, but more than that it's boring. If you have a bad guy who is pretty much unstoppable, after a while he or she stops being intimidating and starts being tiring and slightly goofy. Slasher movie villains tend to have the same problem, although not so much with martial arts.
Look at a character like The Doctor from Doctor Who. Not a villain, obviously, but he's painted as being a nigh unstoppable force within his own story. However, he pretty clearly has limitations. He makes mistakes, there are things he clearly cannot do, he's capable of being defeated and tricked, and has to suffer the consequences of loss sometimes. The reason he comes of as unstoppable, however, is because he never gives up and is incredibly clever and resourceful, so he is often capable of turning defeats into victories. And because we have seen him fail before, it still keeps it exciting.
The same should be true with villains like Drakon. Sure, paint him as an unstoppable force, but actually show him having to work for his victories, don't make them unrealistically easy. Make him an expert fighter, but give him realistic limitations, let him get tired and injured, let people he's fighting get hits in and get the drop on him sometimes. And also, make him fight dirty. The greatest fighters in the world aren't the people with the fanciest moves, they're the people who win fights. He should be biting people, breaking their arms, collapsing their windpipes. The fancy stuff is just dancing, it's good for practice and it's good for exercise, but real world fights don't usually last more than five seconds unless both parties are exceptionally skilled, and even the ones that end without deaths end with some nasty injuries.
I'm not saying he's a bad character, I think he's really cool. I like the stoic hit man thing he has going on. I just don't like part of the presentation. What makes him this unstoppable juggernaut should be his skill and willpower, not pseudo-mystical fighting skills and a magical "everything is easy for me field."