Originally Posted by horatio
Tolkien. The line is uttered by Gandalf when Frodo claims that Gollum deserves to die.
The closest to this in Treklore might be Picard changing his mind about Hugh in "I, Borg" and sparing his life.
But the beautiful thing about that story, and we have discussed that before, is that the ethics involved are neither simple nor cut and dry. A very strong argument can be made that Picard's choice cost billions their lives. Actually, trillions. The Borg destroy entire worlds at a time. You could very easily argue that every world destroyed from that point on is at least partially on Picard's hands for his failure to act.
Why TNG, at least the show version, worked so well was that when they presented us with these types of dilemmas they always made sure that there was a strong counter argument to be made.