A loyal, although not too bright, subject of The Master, Luke, before meeting Buffy, has only come across one other human that has fought him and lived, and then only because they caught him sleeping!
At the coming of The Harvest, Luke becomes the vessel for The Master, and, taking over the Bronze, starts taking his victims, one by one. Buffy, however, has other ideas, and though they fight evenly matched, she gets the upper hand when she smashes a window with a light behind it and convinces Luke that daylight has come. While he is distracted by this, she beheads him.