US News & World Report has one of my favorite pages on the Internet:  The Ten Worst Presidents

It features a picture and description of each of what they consider the 10 Worst.

James Buchanan

Warren B. Harding

Andrew Johnson

Franklin Pierce

Millard Fillmore

John Tyler

Ulysses S. grant

William Harrison

Herbert Hoover &  Nixon

Zachary Taylor

There are many different opinions on this.  Some even put JFK and Reagan at within the top five WORST. http://www.usnews.com/usnews/news/articles/070216/16president.conclusion.htm

As I sort through these lists on the Net, I noticed that President James Buchanan finds his way on the top of the worst over and over.  Here is what US News & World report said:

A Pennsylvania-born Democrat, deeply devout in his faith and the only bachelor elected to the presidency, Buchanan rejected slavery as an indefensible evil but, like the majority of his party, refused to challenge the constitutionally established order. Even before he became president, he supported the various compromises that made it possible for slavery to spread into the western territories acquired by the Lousiana Purchase and the Mexican War. (Particularly hurtful to the cause of restraining slavery’s spread was the Kansas-Nebraska Act of 1854, for example, allowed settlers to determine the status of slavery in their proposed state constitutions.) In his inaugural address, the 15th president tacitly encouraged the Supreme Court’s forthcoming Dred Scott decision, which ruled that Congress had no power to keep slavery out of the territories. More damaging to his name, though, was his weak acquiescence before the secessionist tide—an unwillingness to challenge those states that declared their intention to withdraw from the Union after Lincoln’s election. Sitting on his hands as the situation spiraled out of control, Buchanan believed that the Constitution gave him no power to act against would-be seceders. To his dying day, he felt that history would treat him favorably for having performed his constitutional duty. He was wrong.

Consistently among the best are Abraham Lincoln, George Washington, Franklin D. Roosevelt and Thomas Jefferson.

http://en.wikipedia.org/wiki/Historical_rankings_of_United_States_Presidents