Nightmare Fuel / Civilization

• The "Global Warming" sound snippet in Civilization IV is extremely eerie (and for some reason also plays when the Liberalism tech is first found or when the globe is circumnavigated for the first time). Perfect to illustrate your planet slowly becoming a deserted wasteland, as whenever it strikes a tile is turned into a desert tile.
• Even Civilization IV can be made scary, or at least really freaking ominous, as shown in the intro to the Beyond the Sword Expansion Pack. It's pretty much a history of warfare and communications, and the last part concerns recent times. JFK looks at a photo of a Russian plane stolen by a spy, sighs heavily, and picks up the red phone. Fade to an alarm going off at a nuclear missile silo, where the missile is lifted up and the silo doors slide open...
• The Afterworld scenario for Beyond the Sword. It has incredibly ominous and unsettling atmosphere and music and deals with a Zombie Apocalypse made up of Aberrants created by an Eldritch Abomination.
• Moctezuma in Civilization V is an incredibly ominous figure, even if you're at peace with him. He stands before a burning brazier (which, in Aztec tradition, was used to burn human hearts), and each statement he makes is backed up by a cheering (or booing) crowd. When he declares war on you? Loosely translated, what he's screaming is, "Die! DIE! DIE!"
• Apocalypse Mode in Civilization VI. For starters the game will periodically have "Appease The Gods" competitions which require you to sacrifice military units, meaning that Human Sacrifice is accepted by all religions here. But when climate change hits Phase VII, the comet strikes begin, and continue almost every turn, until the world is utterly destroyed.
  • The animation for a comet strike is particularly terrifying. A ball of fire slowly descends towards the target hex, which is often a city center. There is nothing you can do to stop it. And when it hits, it destroys everything. A city center that gets hit will wipe out the entire city, wonders and districts included, leaving no sign of its former existence. And you can't even rebuild on the original site, as there is now a massive crater there.