There is a distinct advantage in raping and killing. Spreading fear. If villagers have to worry that they will be killed at any moment by bandits and their children forced into a life of violent vengeance, they'll give anything to anyone who promises to somehow stop the chaos. Perhaps even if the poor sheep are dimly aware that those who can stop the devastation are also responsible for causing it.
Now, of course, a lawful evil person starts conscripting stormtroopers at this point, while a chaotic evil person has all of the village elders killed, and goes around collecting tribute at random. Of course, being under the heel of a tyrant or a warlord is still better than what those bastards would do if you didn't pay the protection costs.
The real issue isn't what you can accomplish by spreading fear and misery, but why you want to do so. For my character, he wants to get revenge against his father, and honor his Goddess. Perhaps when he's the ruler of these lands, he can free people from their quaint notions of racial purity, and reorganize society to live in harmony with the phases of the moon, banning slavery and prostitution. (there will be no need for harlots when all sexual behavior is considered acceptable)
The only real problem is dealing with those pesky "hero" types, and possibly that little voice inside of you that tells you what you're doing is wrong.
Better not tell anyone about that, if you don't want to get eaten alive by your companions.