In my lifetime, Biden is the biggest idiot but Carter takes the prize for the worst. His administration's inability to correct economic issues crushed thousands of family farmers and started the loss of domestic manufacturing decline. It was a really horrible time.
Historically, we've had some really bad presidents. Wodrow Wilson was a particularly horrible person who had a Progressive Movement agenda which we are still dealing with today. The radical left road was built and greased by Wilson on purpose. On top of his moral and ethical failures, Wilson basically began the Administrative State, negotiated the start of the Federal Reserve and the our income tax system. In my opinion, Wilson is the absolute worst president ever because of what he accomplished and pushed into place...it radically changed the USA and we've never recovered. The administrative state ideology he managed to implement was planned to grow...and it has. Plus he was racist as hell.