Find out all their credit card/online banking information (they won't need them when they're dead), find out which ones will most likely reward/worship you for sparing them, cash in, use resources for whatever you want (including, but not limited to, basking in filthy lucre). Or were you looking for an altruistic solution? (In which case, pick some arbitrary criteria for whom you like best, or who you think will most improve the world, and go with that.)