My whole life, I have wished for this sort of an event.
I always said that if I had the button that would break the vial, or whatever, I would like to think I would do it, even with no guarantees that I would be a survivor. Not to blow up the planet, or kill the biosphere, etc- just to reduce the human population by a huge margin- at least 90%, but more preferably 95%- or even 98-99% still leaves 700,000 people, and seven hundred thousand people isn’t a tiny number, although it is small for the planet.
Of course, after I became a father, any pretentions that I might risk the kiddos, or even myself as a guardian of those kiddos- became a stupid thing I said as a young adult, immature and stupid.