
The NPC |

Have there been times in a game where the DM put you in a situation where at the end of it they had to go "What have done?" "Look at what we've done?"
For example: In one game I ran I ended up setting things up that the only way out and to resolve the situation was small scale genocide. All the characters felt... Well let's just say that the least religious member of the party felt the need to go into a small shrine and pray about what they had done.

Malignor |

In a modern superheroes game, the party screwed up plenty of times, with some crazy consequences.
- Stirring up a hornet's nest of possession spirit demons, causing the deaths of hundreds when a demon used a passing airliner as a kamikaze against them.
- Killing a keystone NPC in a fit of unthinking, vengeful anger. They did this in Rio Dejanero, which resulted in a portal opening to hell. In order to contain the spewing forth demons, they had to overload a nuclear reactor in Rio and cause a big, dirty meltdown, killing a few hundred thousand people (instead of tens of millions if they didn't act fast).
- Crashed the ISS (International Space Station), and actually rode it to earth.
- Half-failed in saving the world against a vast armada of aliens (billions). They wiped out enough aliens to stop total sanitation of all life on Earth, but there was still enough to wipe out civilization and kill 70% of the human population.
Luckily, after all this, they figured out a way to travel back in time.