The title holder for that dubious honor must be Abraham Lincoln. He might have been qualitatively hated as much as quantitatively. After that maybe people thought rudely of Herbert Hover. President Trump is hated by Democrats, yet that is very partisan. They hated Richard Nixon equally well. George W. Bush was badly thought of by many Democrats and even some Republicans.
People even hated Ronald Reagan. Riding a Greyhound bus from Reno circa 1981 I remember a guy with a Bohemian accent saying aloud the first ten miles- “Ronald Reagan, Donald Duck, Ronald Reagan, Donald Duck…”