I think that "important things" are anything that helps ensure the survival of humanity. This doesn't really help narrow the field, as it is so all encompassing. At the moment, I feel that the most important thing is colonization of other planets, and preferably other star systems. My hope is that by 2250 there will be interstellar colony ships en-route.

The disaster would be good for the species, but bad for individuals. The species is more important than any number of individuals, so such a disaster would be of net benefit.