When you encounter a Witch in Left 4 Dead, the best thing to do is probably to switch off the lights and leave her alone.
But what to do when the AI director decides to put her straight on your way and the only possibility you have is killing her?
Most of the time, the player who wakes her up is attacked and heavily damaged.
How to avoid her claws? Which strategy to use? Are there any strategic differences between Left 4 Dead 1 and Left 4 Dead 2?
Well, when I play with my regular team mates together, we mostly avoid killing the witch. But if you absolutely need to, there are two ways:
Fire and kite: Unless the surroundings/terrain is flat wide area with no place to hide or climb, let one with a mid/long-range weapon shoot the witch and start running around IMMEDIATELY. While she's chasing the guy, the rest of the team unloads on her with whatever they have. Depending on difficulty she drops dead in less than 10 seconds. Don't try this on Expert, especially if your team is not good at tracking targets while firing.
Crowning: If on campaign, the one player with the auto-shotgun gets near and gets the fast kill. On expert, it is possible to use the shotgun, but is also very risky. If the first shot misses a single pellet, you're dead. So, if you have no other choice and only the shotgun at your disposal: Get real close and aim for the chest, AS SHE'S STANDING UP. I do it like this: I get close to touch her, crouch and keep my aim on the head. As she starts standing up, I pull the trigger the moment my cross aim is at the middle of her chest.
On versus, a good team usually has already set up a trap around her, so be extra cautious. Don't even try it with the shotgun. If you miss the first one and there is a boomer around, you're going down pretty fast.
If you are soloing, and NEED to get that witch off the street, you can also use the sniper rifle from a safe distance. The first shot HAS to be headshot, which causes her to stumble and give you about two extra seconds to unload further.
That's it.
UPDATE: As of December 3rd, 2010 Update, the witch can't be killed by crowning (1 shot in the head with the shotgun) in Realism Versus. All other methods still work, though.
If you can sneak up behind the witch with a shotgun, one point-blank shot to the head will kill her. It's a dangerous game since you have to get so close, but it is definitely possible. With practice you will be able to do it consistently.
If that is not an option, then you should follow Arda Xi's advice.
My usual strategy is just throwing a molotov at her and running like hell.
Another strategy (especially when playing with friends) is to set up one guy with a sniper rifle standing far away, he shoots the witch initially while the other 3 are nearby, and they start shooting her. Depending on how far the sniper is, that should give you enough time. This works because the witch ignores anyone not triggering her.
You need to learn how to crown the Witch. With practice, you will be able to kill her every time with deadly precision and consistency.
To practice, bind a key to use the following command:
sv_cheats 1; z_spawn witch
If you don't know how to use console commands, you can read about them here.
sv_cheats 1.
For L4D2, Chainsaw is a great weapon for taking out witches. It has the highest DPS of any melee weapon and can easily kill a witch before she has the time to do her normal react-turn-kill scheme.
I have a strategy to fight against witch.
If I meet the her on my path and there's no other way, so here's what I'm doing to treat her..
But don't do this if your stamina is below 50. She probably could reach you.
Have a nice try.
One approach to easily dispatch a witch that isn't mentioned in any of the existing answers involves frag rounds. Remember that they stun special infected, including witches.
So, if you have frag rounds, and if there is enough room,
That will do the job if no molotov is available and nobody on your team knows the cr0wning technique. The fact that this approach works is actually a nice incentive to carry frag rounds with you instead of deploying them as soon as you find them.
Edit: with an automatic weapon, you may even be able to kill her by yourself. See this video.
If there happens to be an explosive gas canister lying around, place it next to her and then shoot that. Has the duel affect of dealing damage and waking her up, and then have everyone shoot at her.
Of course, this doesn't work quite as well if she is around a corner and you are unable to shoot said canister in a manner that will set her off....
A "will not fail" method is this one (required to be at least 2 players):
The first hit will make her stand up (if seated) or push her back, and you'll have 2/3 sec to kill her. The untargeted player can push her back with right-click, it will give you some more time.
If everything goes well (aka "you're hitting her in the head"), you does need 3 hits to kill her, it's an easy task, even in hardest difficulty mode.
A more cowardly method would be to set her on fire or alert her from a distance then run to the nearest room and barricade yourself. She takes a couple of secs to break down the door but your allies should shoot her to death (those with bad aim might shoot the door down). If the witch is sitting in the way, find a gas can and place behind door before barricading yourself. She will blow up door and gas can and lose you as her target (she thinks the fire startled her).
I would take an auto shotgun and shoot the witch in the back of her head, maybe on the top or middle of her back and shoot ‘till she drops dead, I recommend the auto shotgun because it fires WAY faster that the chrome shotgun. Also this works on both l4d games.
Here is my strategy with a sniper rifle.
