Easily Willow. Willow can kill things with magic and from a distance too. She could kill them before they could even see her.
But, as I've mentioned today, questions like this do not belong here. First because the answers feature is not for matters of opinion, it is for questions of fact. Second, this is the Buffy spot. Many people here do not like Twilight and do not want to hear about it. Questions involving Twilight belong on the Buffy vs Twilight spot, not here. Here is a link to that spot for you:
link