Bush II, though Reagan is close.
Harding. What the heck's wrong w/ Reagan?
He set up the final end of the Soviet Union, reinvigorated capitalism, reestablished the US military and lowered taxes. In Opebo land, those are all bad things.
First, I'll respond here. Let's see: He actually nearly started a war with the Soviet Union and if Russia had had nearly any other leader, but Gorbachev, a war easily could've been started. He created a massive deficit (which Republicans are simply famous for) and led the way to an economic recession, massively expanded government in the one area that truly needs massive budget cuts-the DOD when we spend an obscene amount on defense for nearly no true purpose, and lowered taxes which helped caused the troubles above.
Therefore, though Harding and Reagan pull very close seconds, the one man who lied the most, caused the most deaths, and did the least good is the true worst president. George W. Bush carries this "honor" in my mind. No other President caused so many deaths for such a meaningless cause and lied about the reasons for it. Now the Vietnam War at least had a shred of legitimacy since Communist expansion did slightly threaten our interests, he also did good things that could make up for his serious mishaps. However, Bush has simply done sh*t.