The question is rather subjective, I guess. Because the answer will depend on the person being asked. However, it might be interesting see something that is commonly extremely negative.
Negative in the title is meant in the sense of emotional negativity/repelling/unpleasant/scary/depressing/etc.
You do not have to point out a human being or an event. Your answer could be an abstract one.
My answer could be God/creator/whatever if she/he/it ever exists. Perhaps, it is the exactly opposite, who can know for sure?
I wonder whether humans can make something so negative that negative creates some sort of an emotional black-hole.