The horror, the horror (SPOILERS)
As this movie progressed, I went back and forth over who was the biggest, most vile scumbag, Leo or DeNiro. Of course, the prize went to Deniro as the architect of the scheme to kill off the moneyed Osages "by any means necessary," whether by guns or exploding houses or slow poison. Leo is a close second in the scumbaggery. He kills his share and even tries to do away with his own wife, Mollie, by injecting her with poisoned shots of insulin for her diabetes, of course provided by the King, Deniro.
The horror, as Marlon Brando uttered at the end of Apocolyse Now, might have been an apt title for this film.