Don't play Versus if....
Don't play Versus mode if...
you can't lose,
you ragequit after one map,
you can't wait 5 minutes in a lobby and just spam "GOOOOO!" in chat all the time,
you just want a quick trolling with Special Infected and play Survivors like poop,
you don't know the map with all its chokepoints and killspots,
you don't know that you can go back to ghost mode and respawn as Infected,
you keep on running if you hear the tank music,
you don't share pills or medkits,
you have less than 100 hours in campaign,
you blame the team for your mistakes,
you rush ahead or explore empty rooms,
you can't crown a witch,
you play the finale as Infected and leave when it's time to play Survivors,
you attack alone as Special Infected,
you don't know the right order for saving survivors, chasing after jockeys while the hunter has a go at the all-you-can-eat-buffet,
you instantly spawn as Infected, not waiting for the last moment to surprise survivors,
you act like an antisocial jerk who doesn't care about your team,
you pounce somebody as the hunter with 3 survivors around them,
you hesitate as a boomer, not creating opportunities for your teammates,
etc, etc, etc.....
Seriously, this list could go on and on and on and on like this.
It's so annoying when you want to play a complete match and every round 2 guys in your team ragequit. If you can't lose, don't play, if you want just some quick mindless action - play Modern Warfare or some other poop.
Feel free to add to this list, I'm sure I've missed a lot of the massive stupidity that jumps at you when playing L4D2 with random players.