Ask Lemmy

Since you left room for interpretation I have to mention Factorio :D

Disco Elysium's protagonist is a walking disaster and there are a lot of ways you can play him. Honestly playing him as a totally morally upright professional is one of the harder ways to play. You definitely don't feel like a hero while you're playing

Saints Row games. They're like GTA, but increasingly over the top in their parody. You're the boss of a criminal gang. 2 is still "normal parody" and a bit dated, 3 jumped the shark while doing a kickflip with a jet ski, 4 is even more insane.

Sleeping Dogs you play as a cop, but you can betray the law and side more with the criminals.

Warcraft 3 (old but gold) - the human campaign of the base game gets you from a hopeful young paladin prince into a cold, vengeful psychopath; the following undead campaign is said prince (well, king now) finishing the job of killing everyone and further fucking everything. The expansion has 3 extra campaigns, none with "good guys"

Divinity Original Sin (1 and 2) lets you play as big of an asshole as you'd like. Of the Elder Scrolls games, Morrowind is the one that lets you be the biggest bad guy around (you can still finish the game even if you kill every important npc and break every quest)

Payday 2 (dunno about 3 since it's been called out for being a phone it home version of 2) but yea... you're %100 not the good guy at all. You're a thief robbing banks and peoples homes.

Spec Ops: The Line?

Spec Ops the Line is probably what you want. It's not open world, but the story is excellent.
Bard's Tale is old, but the story is fun and you aren't really a good guy.
Scarface is a GTA reskin that retcons the end of the movie to have Tony Montana live to build a cocaine empire.

The Tropico series of city builders, you are the dictator of an island.

I've just started The Necromancer's Tale, which lets you explore a minor noble's fall from grace into (I think) lichdom. Just came out last summer

Civ6
Lets get to war

Evil Genius.

Not even one mention of Prototype. What have the world become.

The Dark Queen of Mortholme. You play as the boss, repeatedly killing the hero who comes back stronger and more skilled.

The GTA series might be a good example. All of the protagonists of the games commit exceedingly worse crimes as the game progresses but they're made to be sympathetic since they just want success in a world with not much other opportunities.

Games with karma systems may work as well if the bad option isn't overtly evil. I'm thinking games like Dishonored, Fable 3, Undertale, or any Bethesda game.

Anti-hero protagonists like Kratos from God of War, Arthur Morgan from Red Dead 2, and V from Cyberpunk could also somewhat fit the bill.

Destroy all Humans, Call of Duty, Bioshock

Some of the better RPGs allow you to play as an evil guy (equally fleshed out as the good guy playthrough), e.g. Baldur's Gate 3 (it even has a special evil background storyline called The Dark Urge) or (some of?) the Mass Effect titles.

Cult of the Lamb is also a great game where you play a cult leader. Although the game's design is strong on the entertaining/funny side, it's kind of dark also.

Stellaris is a grand strategy game where you can play anything, from a ruthless ruler trying to destroy the whole galaxy to a pacifist trader.

This might produce some arguments, but The Last of Us. Joel is far from a good guy. This is established in the first few minutes of the game and you get enough "hints" about that throughout.

There's actually a pretty new video about that on Second Wind: https://youtu.be/fY1FsMK_cos

Other more obvious games are many many Star Wars games where you can either choose or outright start as the bad guy, like TIE Fighter, the Jedi Knight series, Knights of the Old Republic 1+2 + The Old Republic, Squadrons, those Battlefield games and the Age of Empires clones (can't remember the names) and Force Commander as well I think. Oooh and Rebellion.

Dark Souls 3. NO ONE can convince me you're the good guy in that situation. It's a shit world that ISN'T worth saving and the people who all realize this are the only ones that can save it and refuse to. so your job is to force them to save it.

All you have to do is read the lore on Yhorm and then tell me you're the good guy.

Mouthwashing.

You could do a durge run in Baldur's Gate 3. Maybe also Hitman, but I think that's more anti-hero.

Life and Suffering of Sir Brante (and the upcoming sequel, of Prince Jerian) sees you play a character who is generally morally neutral - you choose your own path and can absolutely "evil max" and it has benefits sometimes.

Entropy Zero 2. It's a mod of Half-Life 2 where you play as a combine soldier and it's actually very well made for a mod.

Any strategy game while you are evil laughing nefariously.

The Witcher is quite famously morally grey, with no "good" choice to many of the major decisions.

Well, I may as well keep plugging my current obsession, Warhammer 40k: Rogue Trader. It's a CRPG somewhere between BG3 and XCOM in gameplay, with a grimdark-flavored splash of Mass Effect.

You have 3 "convictions" that many lot of your decisions fall under. Iconoclast is kind of your standard good guy, but maybe somewhat naive trying to be that good guy in the Warhammer verse. But more relevant to you are Dogmatic and Heretic.

Heretic is pretty much evil as far as I can tell. Chaos worship and slaughter for power. Dogmatic is more like Judge Dredd, maybe? You make some harsh fucking decisions as dogmatic, like liquefying a few thousand people to power a computer you need to use, but you are doing it for what your character truly believes is the greater good of the Imperium.

Pathfinder: Wrath of the Righteous, Owlcat's previous game, has some baddie paths too. You're still fighting demons, but it's more of an evil vs evil in some cases. Especially Lich or Swarm.

Overlord, the first game