A good argument can be made for FDR being the worst president. Among other things, he turned the federal government from a relatively small organization into a huge, money-devouring monster.
But FDR does not get my vote, as he was an incredible war-time president. The stakes were high, and almost everything he did there was correct.
Self-preservation was his primary motivation, and he and the leftists even accused the Republicans of aiding the Germans during his last election campaign.