Can you list your favorite game where it is good leadership to be ruthless and un-ethical in video games?

Grad Theft Auto.
You’re having sex with, then killing prostitutes, selling drugs, stealing cars, running into cops, all the typical anti-republican urges.

It’s not a video game, but I suggest Diplomacy. It’s nearly unique among boardgames for involving no luck at all. Two or more armies versus one army wins every time. One army versus one or more armies results in a draw. Between each turn is a limited period allowed for discussion between all the players.

What makes the game interesting is that in order to win, you need cooperation from other players. Yet every player knows that to win, they must ultimately betray every ally. So every player is trying to convince others that they can be trusted this turn, really, honest-to-gosh, all the while planning to ultimately back-stab that person—who is of course wholly aware of this.

It’s a simple game with simple mechanics, but promotes utterly ruthless manipulation and requires masterful psychological manipulation. The game has in fact been used for decades at West Point to train US military officers in the realities of real-world political diplomacy.

All of Illwinter’s Dominions and Conquest of Elysium games, which include a variety of would-be gods, cultures, and life/unlife-forms to play as, some of which are extremely evil and destructive.

Some nations pursue blood magic, which means sending blood hunters into your own population searching for good people to convert to blood slaves for sacrifice in magic rituals to summons demons, rains of toads and blood, cross-breeding experiments, etc. Strategy involves figuring out how to maximize your harvest of blood slaves, usually with a preference to not incite too much unrest and revolt from your people.

Some nations are even less interested in the survival of their own population, or even against it. Not to mention everyone else’s population. The Ashen Empire version of Ermor, for example, wants to spread its magical domain as strongly as possible, and that domain kills off the population. They basically want the whole world to die and serve them as undead and reanimated servants. The more people die, the more bodies there are to reanimate as zombies, and the more death magic resources there are, and the fewer resources there are for living people to resist your domination.

Or you can play as various Lovecraftian Cthulu-mythos-type monsters, spreading insanity and bizarre monsters summoned from other dimensions.

Or you can open up gates to Tartarus where ancient gods have been imprisoned for centuries, to unleash on the world.

Or you can open gates to various other hellish planes and apocalyptic forces.

Or you can lead one of various types of forces of nature magic, and try to wipe out all other civilizations using armies of animals and magical creatures.

Or any of dozens of other approaches. All with a lot of effort into having the proportions and the way things work and interact make sense and be self-consistent even though the things represented are often wild. Though there are also more “normal” forms of conquest, destruction and domination like knights, armies, spies and priests.

All rather nicely researched and reinvented. At least one of the authors is a professor of ancient religions.

Dungeon Keeper.
Doom.
Pokémon.

Your question reminds me of a game called Beholder. You are a small-time hotel owner and you are in charge of your hotel and everyone who comes there, so that somewhat qualified as leadership. The thing is, you are in a country with North Korean dictatorship and your real job is to make sure no one is “impure”. The goal is to collect as much money as possible to pay the bills, and if you run our of money you are dead, and the government pay you for “purifying” the hotel. But you wouldn’t want to bust your guests because you know you are living in an oppressive society and most of the time your guests don’t even do anything wrong. But good luck maintaining your morality, the bills will keep coming up and your family will start demanding insane amount of money as the game goes on. I remember at one point the most moral solution of the game is to buy fake ship tickets knowing fully well they are fake, and charge big money from a couple who want to defect, only to learn later that the ship sinks and everyone dies.

In a way the game does force you do go for unethical methods to survive. But I don’t think the goal is to glorify immoral behavior. The game is simply trying to show you how horrible it is to live under dictatorship.