I think perspective of the individual really has to come into play on this one. But putting aside all social, financial, and domestic issues, I would say Harry S. Truman for the sole reason the he is the only president who has had to make the decision to use nuclear weapons. I cannot even begin to imagine how a decision like that would weigh upon you. Even a president who makes the decision to go to war is sending soldiers to fight other soldiers who have been trained to have a fighting chance. Dropping a nuclear bomb on a city causes the ultimate collateral damage - 100% collateral damage. Making the decision and living with it afterward has to be the heaviest burden any human being ever has to bear.
Redneck, hillbilly, fundie, Bible thumper, cracker, split tails, geezer, loon, xenophobe, islamaphobe, and homophobe are not words of tolerance.
I agree he was a great president. Fierce independence alienated him from his own party, causing him to lose his attempt to become the Republican nomination for the presidency in 1912.