My initial instinct is to say Batroc, but Rory is one seriously tough customer (though Batroc is also extremely durable for an un-enhanced human) and, while not necessarily a traditional martial artist, has shown that his own fighting style puts him right up there with some of the top tier fighters in the CW DCVerse.
I can kind of see Batroc doing all his fancy flips and things, and Mick just kneeing him in the crotch as he lands. He's not above fighting dirty when necessary.