> Both the examples from LotR end up justifying mercy. Gollum's actions at Mt Doom end up forcing the destruction of the ring *and* prevent Frodo from turning to evil. Also, Wormtongue kills Saruman when nobody else is able to do it. I got the impression, in the book, that Wormtongue's slavery to Saruman was what eventually sent him over the edge and gave him the sheer viciousness and hatred to kill Saruman, when everybody else was still capable of being swayed by the wizard's persuasiveness.

Not to mention that, without Wormtongue's meddling, the company wouldn't have gotten the palantir of Orthanc, which is significant only in insinuation. And in that they got a MAGIC ITEM, which, as any fantasy gamer can tell you, is basically the whole point of life in a fantasy world.