Ah... these guys lol. Usually I just ask how many fights they've had, as soon as they back up from the "i'm the best in the world" shit and reply "None", it's generally on the right track to shutting them up.
Also enjoy when sparring with them, to infact not try to submit them, but to make it so obvious you're not trying and coach them on how to beat you. Often humbles them a bit when they spend 15 minutes trying 100% to submit you, even as you teach them how and they still can't.
I did recently break my rule on rookies and lost it with one guy. I'm 5'8 130lbs, guy was 6'2 230lbs and despite repeated warnings from me n guys he sparred with first, he kept trying to knock me out with full power swings... so I chopped him down with leg kicks and a brutal liver kick and he hasn't been rough ever since