If you mean worst as in “did the most damage", Reagan goes to the top of the list, followed by Trump and then possibly Wilson (WWII came straight out of Versailles), Then a tie between Hoover and Bush II. But Hoover likely was just in the wrong place at the wrong time (look at what he did for Belgium post WWI).

If by worst, you mean 'most corrupt', I'd have to go with Grant (not corrupt himself, but pretty much everyone else in the administration), then Trump (everyone including POTUS), then maybe... Taft?