What kills a wolf?

You can kill a wolf by putting a bullet through the skull with a gun. In today's world, that's how most wolves are killed. However, you can also get one with a cross-bow or bow-and-arrows if you get close enough and are a really good shot.

In extremely rare (or, rather, unheard-of) cases where a wolf is attacking you you can kill one with a lance or a knife. If it's rabid, just make sure you strike first before it strikes you.