[The Squatter of Amon Rûdh]

It seems to me that were characters in Middle-earth just to exhibit the deadly sins then I could put these examples down to simple ubiquitousness. There does seem to be a moral framework involved, however, in that the sins lead to catastrophe in all of the cases that I've seen quoted above.

Of course the villains of the piece would exhibit the sins, but when otherwise "good" characters (ie those opposed to Morgoth) fall prey to them the results are normaly disastrous. Now, to my mind it only follows that sin leads to destruction in a moral system built around that concept, so it seems reasonable to assert that Tolkien had such a system in mind. Admittedly I'm still looking through the Letters and associated literature for more evidence, but I was hoping to inspire some debate, rather than just a list of examples.