Well, the worst song of all time has been sometimes declared to be "McArthur Park" as done by Richard Harris - but doggone if I don't like it.
For pure stupidity, I'd go with "? and the Mysterians" and "96 Tears." I don't think it used more than three notes, and I have no idea why one would cry 96 tears.
Mildly confessional: When Grandma and I were dating, we went to a concert by the Ides of March. Their signature popular song was "Vehicle," which was a creepy kind of thing.....
BUT they were excellent! Great brass section. They did a send-up of bubblegum that was hilarious. And they just put forth really good music. The lead singer sang (obviously), and did some dance moves, and got the crowd going, and played his guitar. With the loathsomeness of "Vehicle" aside, they put on a really good show.
Okay, okay, this is a thread about bad songs. "Butterfly of Love" was tragically overreaching, and Neil Diamond's "I Am Me," or, "I am I," or, "I Am Myself," whatever it was, was a dreckslog.