Radley Balko picks my least favorite American president for dishonor:

Woodrow Wilson. Jailed political dissenters, created the Federal Trade Commission, got us into World War I. He also enacted the first federal income tax, the first modern military draft, and the first federal drug prohibition. Wilson also re-segregated the federal government. When blacks protested, he told them to consider segregation a “benefit,” not a debasement. An all-around loathesome human being.

I agree with Balko’s assessment except on the World War I point, if only because I think U.S. involvement was inevitable based on rather boneheaded provocations by the Central Powers, most notably the Zimmerman telegram.