I don't mean any dead people. I mean people who were so deplorable that they made the world a better place by dying. I'm going to ignore the ones that are so obvious that speaking ill of them is not even controversial, such as Hitler, Stalin, and various serial killers.
Some of the dead people about whom I have nothing good to say include (listed alphabetically):
Morton Downey Jr.
I'm sure I forgot several, but I think that this list is a good start.