4. Franklin Pierce
Pierce was a weak head of state who could easily be manipulated by those around him. He, therefore, made several poor decisions that led to terrible consequences.
For instance, he signed the Kansas-Nebraska Act, which gave the green light for slavery to extend into new areas. This outraged many northerners, triggering the creation of the Republican Party.
It is believed that Pierce suffered from both a lack of conviction and bad timing. The once-popular candidate became the first sitting president to be denied re-election by his own party.
Ultimately, he let himself be intimidated by Stephen Douglas and signed the Kansas-Nebraska Act, which paved his path toward his downfall.