There are a few that would qualify in my book. But the worst would be those that are used to demean others and dehumanize.

Some racist songs from the South would qualify such as Run N----------Run, the Pateroll Will Get You, or I've Got A Bimbo Down in the Bamboo Isle. Some Minstrel shows would qualify. Songs demeaning to women would also qualify in my book such as many "dirty" songs
that are not funny but ugly such as Barnicle Bill the Sailor.
Songs that were employed for negative political purposes would
have to qualify such as Dixie even though as a song, it has a great tune but has been debased by some psuedo-Confederates such as the Klan. The Horst Wessel song might qualify. Jovenetse Primavera from facist Italy might be another.

As to the inane aspects of some popular songs such as "Feelings"
or other bits of treacle, I think that if they don't do damage
and someone likes them then I can't consider them the worst I've heard. This thread is a set-up in that it's a subjective opinion that's asked for, not a critique of the mechanics of songwriting.

But the sexist, racist, inhumane songs for me would qualify.

Frank