I usually take revenge when noobs who are complete idiots and betray me constantly. And I do it with a skillful weapon, unlike theirs. Usually with a headshot with the Human sniper (No Scope). And if I get the chance, which I usually do, I boot them from the game. If they're playing loud music, I just mute them.
BTW, why do they do that? Do they honestly have nothing better to do? That's just sad. But I don't let that get me down. I always enjoy my games and greatly admire the fact that I'm not one of them.