Criminals like Capone are debatable when you're talking about essentially political figures (and yes, Capone was a political figure, too, with his bribes, etc.); but if you start including common criminals like Capone and Hinckley, they get shoved aside pretty quickly by Lecter-esque figures like Ed Hein, Charles Manson, Jeffrey Dahmer, and John Gacy. And let's not forget monster-woman Carolyn Wuornos, the first female serial killer ever identified and captured.
But if you're just talking about political people, you'll see LBJ and the Rosenbergs are already on the list. Huey Long is a good suggestion. And I'd add Henry Wallace, Stalin's man in the 1948 election, and Ayers and Dohrn, James Earl Ray, Huey Newton, Bobby Seale, H. Rap Brown, Stokeley Carmichael, Wm. Kunstler, Mario Savio, Tom Hayden, Donald "Cinque" DeFreeze of the SLA, Jim Jones, Alfred Kinsey, the dynamic duo of Marshall Kirk and Hunter Madsen, Aaron Burr, Alan Greenspan, the Walker family, John Brown, Tokyo Rose, and David Koresh.
And while I'd disagree that Woodrow Wilson, Al Gore, and Harry Reid are significant enough to remain on the list (they tend to drop off from insignificance), I'd argue for Tom Daschle replacing all three of them, for having invented both the Obama campaign (he was its architect) and the government shutdown in 1995 that enslaved so many government check-cashers to the Clintons.
There are plenty of other candidates.