Jimmy Carter... do I
really have to explain it??? I'll just quote NY Jew for you:
Jimmy Carter
Iran, stagflation, gas on alternate days, destroying Nuclear power, his lack of Soviet policy ext.
(though if I can include Roosevelt's early years (gutting the military in the 30's ranks as the worst foreign policy move in American history) he wins) to soon to judge Obama though his actions in the Arab Spring might prove to be worse then Carters
Yep. One great big "malaise."
Sky-high misery index, long lines at the gas pump (dare I use the cliche "pain at the pump?), Iranian hostage crisis, stagflation, stratospheric unemployment... the list goes on and on.
In terms of a person (rather than policy), Carter was one of the best presidents since WWII. LBJ would probably be the worst (horrible racist and political opportunist who only signed the '64 CRA to boost his popularity), followed by Clinton, JFK, and maybe Nixon.
However, back to policy. I think Nixon, Watergate aside, was actually a pretty good president in terms of his policy. As a person, not so sure. But for the worst based on policy, the answer is pretty obvious. The Ol' Peanut Farmer himself, Jimmy Carter.