2. Hard Luck Blues (New Vegas)
Hard Luck Blues is home to one of the hardest moral choices to ever grace a Fallout game. When you're asked by a small settlement to sort out the small problem of their entire water supply being too irradiated to use, you eventually find yourself in the depths of Vault 34, one of the few vaults in the Mojave Wasteland that still has people living inside. At first, it doesn't appear that this will cause any problems in regards to your main mission, as all you need to do is make a few tweaks to a couple of terminals inside the vault in order to stop a leak from spreading to the nearby water supply. However, when you finally find a way to shut off the radiation, it's revealed that by doing so you'd trap the inhabitants of the vault inside the room they're in, sealing the doors and leaving them to starve. To complete the quest you have to choose whether or not to shut off the pumps, saving one group of people by dooming the other. Even worse, when you finally complete the mission and make the decision, you don't receive any Karma points for it. As a result, you'll never know whether you made the best choice, and you'll have to carry around the guilt of knowing that you doomed an entire group of innocent people for the rest of your playtime.