Abraham Lincoln, who invaded and annexed the Confederate States of America, engaged in brutal repression in his own nation, ordered Sherman's March to the Sea, and ushered in the most brutal rape of a nation that the United States--or most other nations, for that matter--have ever engaged in.

Franklin Delano Roosevelt, whose actions prolonged and worsened the Great Depression, and added to Stalin's power, causing problems that it would take decades to solve and cause untold repression before then.
...Wow. I advise you to not put your complete faith in radical websites and the odd book and read a few history texts from more objective sources. If FDR had not put his economic changes in place, WWII wouldn't have gotten us out of the Depression(especially the ones concerning the stock exchange and credit - the biggest reasons for the Depression in the first place). I'd also like to point out that after FDR and Truman, we were already well on our way out of the Depression, well before Reagan.

While I do think Bush is a horrible President, probably in the top 5, he was not the worst.

Andrew Jackson: think Kerry's a flip-flopper? This guy was so much worse. The main reason this guy was nuts is that he completely disregarded a Supreme Court decision and forced the Indians around Georgia to pick up and make the "March of Tears" to the west. He was creditted to have said, "Let Marshall enforce it," or something similarly abominable. He gets my vote for worst president.
Also, on the Tariff of Abominations: Jackson originally got this made a bill solely to make Quincy Adams look bad(because Adams had beaten Jackson at the last election). On the next election, Jackson won because he said he'd repeal the Tariff. When he got in office, he didn't. Talk about underhanded, dirty tactics. He even betrayed his own party(which is why even The Redneck doesn't like this guy).

Andrew Johnson: comes in at #2, this guy completely ignored the South after the Civil War. Instead of reforming the Union, he let the South become poorer and even more lawless. He was impeached on a technicality, but not convicted.

Herbert Hoover: This guy comes in at #3 not for any specific action he did; in fact, the past two Republican Presidents were probably much worse(and would have done much worse in his place), but Hoover had the misfortune to be the wrong President at the wrong time. He did nothing to cause the Great Depression, but he sure as hell didn't do anything to end it. He kept spouting that private charities were responsible for helping the poor, starving families, and was quoted to have said, "If people were dying of starvation, I'd give money to the states." This was after thousands had already died. Refused to hand out government "charity" and only reluctantly lent some money to the states.

Now, for Presidents that I think did a marvelous job:

Lincoln
Teddy Roosevelt
Franklin Roosevelt


Presidents I like even though they weren't spectacular(because they were put in a tough spot or just had a lot of bad luck):

Truman
Grant(a hopeless President, just because he was too honest for Washington).
Kennedy