@divisionbyzero: I believe 1 and 3 have a lot of overlap, and most of 2 is included in 4.

1, 2, and 3 rely primarily on human nature, and while a small number of known 4 events could end us and quickly, my money is on human nature. Alas, I cannot pick 1, 2, or 3 because that narrows it down too much to me. I believe that Humanity's Great Filter will near-certainly be due to its own human nature.

All of this says for the sake of argument that human nature is not a natural or a natural disaster.