The problem is that people don't treat you differently for being evil. Yeah, you might have hitsquads coming after you, maybe a companion or two won't follow you. But the same happens to good characters. There's absolutely no weight to your actions. You can literally slaughter half the wasteland in broad daylight and people will still talk to you as if you're just a typical person. I always end up having evil karma because I steal everything not nailed down and yet I'm still considered a hero by everybody. It's only gotten worse in games like Fallout 4.

Too many games I've seen conflate being evil with being a jerk. Few games let you play the 'long game' where you are specifically nice and cooperative to deceive and manipulate. I think this partly due to decisions being made modular and point to point. Your overall morality then is calculated as some form of average of all the decisions you made. Mass effect series comes to mind.

But if you want to play as a scheming villain the opposite should be the case: you set your primary long term goal (eg taking over a country or institution) and then your actions are chosen in the vein of that goal. And those actions might in isolation actually be seen as beneficial or benign. But you ultimately do them to gain trust or deceive.

I kind of enjoyed how Oblivion handled things as completing Dark Brotherhood or Thieves Guild quests gave you infamy that made good characters dislike you and evil characters like you more. Though there still is a lot of jank in that game (part of the charm imo).