I have a situation similar to this in my school. We have a newer student who is quite crass, and brags about how good he is at sparring and that he was a higher belt at another school. I think many people have seen this kind of person. I am 5'7" and weigh about 170, this guy weighs about 6 feet and about 230. This person would always be telling people what they are doing wrong, even to higher belt levels in a most non-constructive and negative manner. Many times when he talks, everyone else just rolls their eyes. Our instructor has taken notice of this and has had talks with him, but he sometimes still persists. Anyhow, I went to sparring the other day, and I figured he'd be there, now he's always said he was very eager to spar me in a condescending manner that he would own me, etc. Let's remember he's 6', and 230. I am also 10 years older than him, married, kids, etc. I'll admit I was nervous, but I remained calm and loose. I asked him what he is comfortable with as far as contact goes and he was eager for full contact. This is his 2nd time sparring at our school, but if you heard him talk it would sound like the 1000th time he's fought. Long story short, we went 3 rounds. He tried several times to go in on me only to eat jabs despite his reach advantage. He was god awful sloppy and dropped his hands every time he did anything. Long story short, I knocked his helmet off twice, and hit him so hard with a left hook, his helmet spun halfway around his head. He got tired very quickly and I caught his foot twice and pushed him to the ground and mounted him, which is where our instructor ended the rounds. After that, he is MUCH quieter about talking about how great he is. I had a good conversation with him afterwards, and showed him some things he could have done to counter my tactics, as well as things he did well. Even if the fight was a mess for him, its always important to show things he did well, even if he is an jerk. I can only hope he can take that experience and run with it. There is an invisible stripe that you must earn in class, and that's a willingness to be kind and helpful to other people. Sadly, there are places that don't have that requirement, and I personally find it just as important as any technique you could ever learn.