Nightmare Fuel / Shin Megami Tensei I

• In the beginning of the game, you and the Law Hero are imprisoned for asking about the demons. When you break out of your cells, you discover the doctors there are Playing with Syringes and performing horrible experiments on prisoners to create mindlessly obedient super soldiers.
• Coming home to your mother, only to find out it's actually a demon disguised as your mother, who the demon already ate! And then the damn thing taunts you by reminiscing about how delicious your mother was, and wonders aloud if you'll be as good...
• When Thor reveals that a cluster of nukes have been launched with Tokyo as their destination, you don't just get some cutscene of the missiles whirling towards Tokyo and exploding. Instead, you're sent back into the dungeon, and a 30-second timer appears, just to reinforce that Tokyo is about to be obliterated and that there's nothing you can do about it. Thankfully, the Heroine teleports you out right before the impact.
• The Chaos Hero goes straight for the obvious question about the Cathedral of Shadows and tries to manipulate the demon fusion process by fusing himself with a demon. Then he explodes in front of your very eyes!
• The iconic Law theme consists of a very eerie synthesized Ethereal Choir chant that really gives off the vibe that Light Is Not Good.
• The intro of the game. Unlike other RPGs released at the time, which would usually go over some sort of exposition or show off cutscenes, this game plays absolutely nothing until the ATLUS logo, then a unsettling track with choir plays for a bit before changing to an even more unsettling track; a heartbeat-like sound and deep droning noises combined while showing the characters and someone typing in strange code (revealed to be Stephen on the Sega CD version) on a dark screen then cuts to the title of the game.. shown in blood red, revealing in a way that resembles blood trickling across a surface. The intro and title screen alone shows that this is a game not meant for kids.
• Roppongi seems like a peaceful city, as it has no Random Encounters and everyone seems content and happy...but those inhabitants are fact zombies whose spiritual energies are being used by Belial and Nebiros to maintain the barrier and illusion for their master Alice. You meet her and encounter her first use of her Character Catchphrase "Will you die for me?"
• In the final act of the game, after deciding that nuking Tokyo 30 years ago wasn't enough, God pulls a Noah's Ark and floods the entire metropolis, drowning every human who isn't in the Cathedral or hiding in the highest floors of skyscrapers.