Today in Bernie Sanders' presidential announcement, he said that Donald Trump is the most dangerous president in modern American history. What event / which presidents fall before modern American history?

Which president in pre modern American history would someone generally from the left consider more dangerous than trump? Maybe Andrew Jackson, but dangerous isn't really the descriptor that comes to mind.

Obviously in Germany you can't say "Angela Merkel is the most dangerous chancellor in history" and would have to use the caveat "modern", but I can't think of a president who is the obvious American standard bearer for "dangerous" such that one would need to couch am assessment of trump relative to only modern presidents.