The Nature of Evil in Computer RPGs
As for actual, yes-I’m-evil-and-I-don’t care gameplay potential? You can do quite a bit of it in many open world games, although in the case of games like the Witcher series it’s more like ‘being an uncaring jackass.’ Bethesda’s Skyrim has at least one definitely atrocious questline (Dark Brotherhood), and its Fallout series give plenty of opportunities to win the game while still relentlessly being a horrible human being*. And Obsidian’s upcoming Tyranny promises to be a game where being evil is the default option for your character.
But for the most part? Computer RPGs tend to shy away from allowing too many conscious choices for simulating evil behavior. Which makes a certain amount of sense, particularly if you happen to believe in any sort of universal morality. Which most people still do. And that is… somewhat reassuring, actually.
*There is one particular meta-game moment in Fallout 4 that still elicits a reaction to me, every time I play through it. [SPOILERS] You’re sent to the Pickman Gallery to check out a rumor that something bad is happening there -- and there is. There’s a guy there (Pickman) who goes out and hunts Raiders (generic bad guys), then uses their blood and corpses to create horrific works of art. And he is absolutely unapologetic about it, because he’s a serial killer that only kills Raiders. Regular non-player characters (NPCs) are perfectly safe from him. ...And I can’t make my character kill Pickman, because he pretty much does what my character does every day, only I loot my victims for different raw materials. But what I do is OK, because I only kill things that have red-colored names on the screen. And yes, that’s all very awful in real life.