When Benderism Goes Bad

Was reading an old Williamson story ("The Fortress of Utopia" IIRC) in
which the earth is facing some Cosmic Menace and the Plucky Heroes
come up with an elaborate scheme to save mankind which involves
murdering most of humanity.

Things do not go as planned, and it's only due to the survival of some
people which under the Plan should have been worm food that the world
is saved.

So, other stories of this type? In which the heroes must make some
Hard Choice For The Greater Good in which a massive number of innocent
people must die - and it turns out to be a pretty screwed plan in the
actual execution?

Bruce