The next best thing to a dead enemy is a scared enemy...and if properly manipulated, a scared enemy is better.
In combat, if you are facing 100 enemies, and shoot one, you are down to 99. If you get one to run away, the others will think twice, and remember that fleeing is still an option. That means, if one flees and causes 10 more to flee, you only have 89 left.
I say kill 99 and let the one go and tell the ones you don't know about... missing a body part preferably (nothing serious, a finger or ear). That'll do jihadi, that'll do.
P.S. Oh, with cans of SPAM strapped to him as well.