In this section I will cover the Tank and Witch
The Tank is a powerful infected that can be heard coming with its speical "Tank music" and ability to make the ground shake as it comes closer to survivors. The best way to deal with the Tank is to have a Molotov handy and to have all other infected cleared of the area. This is because one single infected can slow down a survivor and spell potential death. As a Tank in versus, you want to avoid everything that you would do to a Tank in Campaign. Make sure all your teammates are helping you out and once the survivors are sufficiently slowed don, this is when you attack. Try to target survivors with Molotovs so they can't use them when they're incapped, but if they have them in hand and ready, be sure to avoid them. Sometimes tricking them into using it like chasing them, then backing off just as they throw it can be a good way to avoid Molotovs. Remember that grouped survivors are better as the Tank can punch multiple targets. If the survivors are too far away, remember the Tank can throw rocks. These arch so be sure to aim a little above the target to compensate. The farther the target, the more you'll have to aim up wards. a 45 degree angle is farthest you can throw, so anything other than that is out of reach of throwing rocks.
The Witch has the same rules with being a survivor in versus or campaign, except there is added pressure in versus as the infected players will likely set a trap around it. A shotgun is needed here for a headshot against the Witch. Remember to aim around the hair/neckline for an instant kill. You'll have to rely on your teammates to cover rooftops and keep the zombies off your back. If another player on your team is executing the Witch, be sure that you are covering them sufficiently. If you are an infected, each zombie has its own role. If you are a Smoker, attack the survivor executing the Witch. Hunters should attack the supporting survivors and Boomer should be somewhere inbetween all the action like throwing bile on the survivor carrying the shotgun and charging the others in attempts to block some bullets and explode more boomer bile.