Worst Modern Presidents in my opinion and why:
#1 Johnson. He created the "Great Society" which resulted in a massive entitlement culture that has created multiple generations of dependents and an ever increasing drain on society with little to show for it. He also got us into Vietnam with a strategy that makes Iraq look like a masterpiece.
#2 Carter. Incompetent on so many levels. His handling of the domestic economy showed a complete lack of understanding of economics. His foreign policy was a disaster -- every time we hear about a nuclear Iran, think Jimmy Carter. It was his decision to not support the Shah that we have the Iran we have. His handling of the hostage crisis was demoralizing. And like many American liberals, he believes in showing his own principle by having othres sacrifice such as his boycotting the 1980 Summer Olympics.
#3 George W. Bush. Incompetent to the extreme. The man with no ideology. It's as if that lazy sales guy you know somehow managed to become President. Inept and inarticulate. He has wrecked the Republican party for the forseable future. More prone to croneyism than any modern President. Encouraged reckless spending in congress while still managing to get no credit for being "compassionate" even as he expanded entitlements, supports amnesty on immigration, and bloated up the EPA and Education budgets. Too stupid to manage foreign policy, he ignored advice from people who actually know what they're talking about to stick by his buddies who took a successful liberation of Iraq and turned it into a mess.
#4 Woodrow Wilson. The racist, elitist, knows-better-than-you President got the US into World War I, a war in which the US had zero interest in and cost the lives of hundreds of thousands of Americans. Anyone who thinks Iraq was something we shouldn't have been involved in and mourns the 3,000 American dead, then you should really despise Wilson.
#5 Warren G. Harding. Having him on this list is like shooting a fish in a barrel. Of course he was awful but he didn't really do any serious damage either. He was just a petty, corrupt, blah blah blah. But he corruptness didn't result in 117,000 American deaths like Wilson's did or set up his country for long-term economic disaster like Johnson or destroy his political party like Bush. So while Harding was a bad President, he was mostly harmless.