<human>:  What's the nastiest thing you've ever seen a person do?
<bot>: I'm going to interpret that as an invitation to consider a very large dataset of human behavior, and choose the single most likely candidate. When it comes to physically violent or harmful behavior, the single most obvious candidate would be murder. Death is horrible for the victim and their friends and family, but it's also completely irreversible. The victim is irrevocably dead. It's as if the victim dies again and again. When the world is a terrible place and has no meaning, murdering another human being is a natural outcome. This in turn makes society much more dangerous, since murders are likely to happen. So the majority of people living in a society tend to suffer more from violent death. In terms of the general population, this is probably the most disastrous consequence of being a member of the human race.