Intentional evil? Probably Andrew Jackson. His low points were very low and he had no qualms about slaughtering his enemies.
Unintentional evil by virtue of incompetence? James Buchanan and Andrew Johnson
Buchanan was clumsy and came into the presidency at the wrong time, so he was pitiful/exusable, but Johnson was just plain bad. He blatantly opposed giving freed African-Americans basic rights like voting. He was not "uninentionally evil." I'd say the two most uninentionally evil presidents were the two northern Democrats who directly preceded Lincoln and who had cool last names - Pierce and Buchanan.
But I agree with you on Jackson. He was just evil, and most likely worse than Trump. There are more than enough examples - him slaughtering Native Americans and British soldiers in the late 1810s, the Indian Removal Act in the 1830s, and much more. What's interesting is that they both had similar base voters - poorly educated, lower class white men in rural areas.
