*Guaranteed* method to get rid of taunt-teamers
I have been holding back on unveiling cheaper tactics for dealing with taunt-teamers (i.e. taunters with the sole intent of teaming), but since the taunters have already revealed cheap methods, I decided to let the cat out of the bag by revealing one of mine:
Basically, it goes like this. If you suspect the room you are entering has teamers in it, wait to see if a crasher starts attacking. Don't let it become 3 vs. 1. Just act like you're a pacifist, so the taunt-teamers will ignore you. "Accidentally" get in the way, but make certain that the crasher was the last one to hit you. Then "accidentally" self-destruct, giving the crasher a +1. As long as you don't make it too obvious, the taunt-teamers might not notice at first. Repeat once more and they are likely to notice this time. :-) Rinse and repeat as often as you like.
Sooner or later, the taunt-teamers start to question their own "rules." You never attacked them, and they generally don't attack unless they have been attacked. Do they now have to break the "peace treaty" by attacking you? Or do they allow you to keep giving the crasher free kills? Either way, you mess with teamers' heads, and at least one of them will ALWAYS leave after that match or the next one. It has never failed for me.
The best thing about this tactic is that you can pick any character -- even one you are not good with -- and it is easy to do. In fact, I recommend entering rooms as Random, so they don't catch on in advance. The last thing you want is to spoil the surprise (e.g. "Oh no, here comes the albino DK again!") After one of the teamers leaves as they always do, you can do as you please. Switch to one of your better characters if you like. Team up with the crasher to frustrate the original teamer or just let it turn into a free-for-all as the game intended. You might even get a fair 2 vs. 2, just like Team Battle, but with permanent teams with friendly fire on. Any way you look at it, you encourage new crashers to enjoy the game and do away with the childish 3 vs. 1 teaming at the same time.
Let the games begin!