Umm, yeah it will. Are you just talking about a quick blast or about holding it on the person. In any dark situation, have a friend (with an E1B or equivalent) hit you with the beam and hold it while "pretend" attacking you. You'll find that you don't see it coming. In a city setting with bright ambient light you might need more output but for the average "streetlight" setting 80L will do pretty well.
As posted above, I can't find the thread that was recently created by a CPFer who tested out various lights, and their "blinding" power.
But the results he got were less than impressive.