The thing with TR and Jefferson, though, is while both have HUGE flaws you can hold against them, most (keyword "most") would argue both did a lot of good as well. (You may disagree--feel free, *I* am not saying they did a lot of good, just stating the pretty-obvious fact most people would defend 2/4 Rsuhmore Presidents.)
And I think the "Most Evil" title, from my perspective anyway, has to go to someone who did all or almost-all evil, with little to nothing redeeming.
Jefferson was a racist and a slave owner, but plenty would point to his John Locke-borrowed Declaration of Independence, the Louisiana Purchase, and Enlightenment idealism as redeeming factors.
Teddy was an imperialist, but he was also a trust buster (though not as big of one as Taft, by the numbers) and did start the first national parks and was a major conservationist to boot.
So both have arguable positives.
That's why I personally like the J. Edgar Hoover or, for my part, Jefferson Davis/the Confederate Leadership as the the Most Evil American(s.)
There's little to nothing to be said in defense of THEM...they didn't declare independence for the nation, weren't an Enlightenment thinker and figurehead, didn't vastly expand the nation's wealth, power, or the overall well-being of its citizens, didn't conserve land or create new economic policies to make businesses more accountable...
One was a gestapo fascist in all but name, and the others tried to destroy the nation and keep millions in bondage (and if it was wrong for Jefferson to keep slaves in the 18th century--AND IT WAS--imagine how wrong it was to not only keep them but actively promote slavery and fight for its survival in 1865, LONG after Britain and others had abolished the heinous policy.)