Status games, why not? At least the purpose is upfront and the weather is nice. Here is a list from right-wing bloggers and here is a list from Bainbridge, both in one link with Bainbridge's comments.
It's bizarre that Jimmy Carter comes out as the all-time worst from the right-wing bloggers and I don't have to tell you who is number two. It's also hard for me to see how Bainbridge ends up with Paris Hilton and Michael Moore in his list of the worst and he seems to acknowledge this oddity toward the end of his post.
The most plausible picks are, I think, any number of political figures behind slavery and its continuation (it's debatable who is truly focal here), Woodrow Wilson, the Rosenbergs, and any number of assassins, domestic terrorists, and serial killers.
Who am I forgetting? Are there focal figures who held back public health advances? Led slaughters against Native Americans? What else?
Who is the worst Canadian of all time?
Hat tip goes to Andrew Sullivan.