Can glory kills be disabled?

I have a strong enemy the player has to kill. Like boss-level strong. But if you fail to glory kill an enemy, they return to 50% health. Which makes a really strong demon impossible to kill. (It does a lot of damage, so you don't spend any unnecessary time up close to it.)

Can this be disabled? Or will I have to use some kind of logic device to set its health low once it reaches that point?