>>4914
As in literal nightmare, I don't know. My first nightmare that I remember was when I was 3 years old. It was about rising lava. There was also a (funny) nightmare I had when I was 8, where I came to school, and it was empty, and then there was an anthropomorphic cow behind me who was going to eat me. In the past few years I have had various nightmares involving a specific group of "people", but I don't want to break rule 9.
Nightmare in a more general sense... it would probably be hell, as in eternal torture (eg. after death). I was raised in a religious household and that disgusting story still hasn't left my mind. If talking about more realistic things, there are too many bad things that could happen, and I can't keep track of them, and I prefer to not think too much about them. But something that I feared a lot during Covid was being forced to take the "vaccine", most likely indirectly (eg. a law being passed about not being allowed to go to any public spaces unvaccinated).