Inherently evil species? My solution
It used to be the case that everyone knew that orcs were bad and that you should have no problem dispatching them in your game. Unfortunately over the years orcs have been given more and more human qualities to the point where some people now feel uncomfortable treating them as inherently evil. An easy way to side-step that is by having the adversaries be various kind of undead. I like to use undead beast-men as the go-to bad guys. I just imagine necromancers casting dark sorcery on flocks of dead goats and sheep, turning them into an army of undead. They are already dead, they have no culture, no feelings and no free-will. You're doing them and the world a favour by destroying them.