Quote Originally Posted by shinta|hikari View Post
I mean, why stop at half? Doesn't make much sense at that point.
Hostages? To leave witnesses of his power? To show he doesn't need to kill more than he requires, demonstrating that he can be as vicious and reasonable as the situation calls for?

I can think of a number of reasons, but hopefully he kills them all and that means he becomes an even greater Demon Lord for it.