My apologies for totally forgetting about this, in the wake of bribing myself to finish Kim.
April's MLLD Award goes out to the Russian guy from Kim who smacked the lama in the face and tears up his Wheel of Life picture that the lama worked so hard on. That was just wrong. I was glad when Kim rolled him down the hill and kicked him in the groin. I would have kicked him more than once there. Although in hindsight, I should probably thank this guy for bringing some action to an otherwise action-free novel. :)
The only other character who came close last month was Cecil Vyse from A Room With a View. I didn't think boring characters qualified as dirtbags so I couldn't really nominate him. :)