Climate change is the other big one, but given two different sources of great future suffering and dystopia, the one that's rooted in premeditated evil in the heart of man is much more distressing to me than the one that's rooted in stupidity and negligence (not that there are no evil parties benefiting from climate change, but malice upsets me more than greed).

But those are just my personal feelings; there's no ranking tragedies, really, and I feel equally powerless against all of them anyway. So take your pick on which one you're going to lose the most sleep over.