Harder Than I ThoughtHmmm ... this'll be a tough one - I don't typically hate music, and usually something I don't like will still grow on me.
Hmmmm going by genera - I'm not a huge fan of country or really hard metal - but I think some of the stupidest crap I've heard has been on the pop stations - something that tweens would listen to - like Justin Beiber or something artists who to pass their crap off as actually rap/hip-hop (I don't even bother to learn the names of the songs/artists) - what a disgrace to the greats that paved their way (<3s me some Sugar Hill Gang and De La Soul ) ;-)
Oooh oooh - I know- Amy Winehouse at some festival (I've seen a couple televised) - what a FREAKING TRAIN WRECK! I even like her Rehab song- just not live *shivers*. And Danny O'Donnell. He's not *that* bad, but suuuuper annoying, and all the old people in my family just love him.
As for a specific song, I'll have to get back to you. I never cared for Lee Greenwood's "Proud to be an American" - not that I hate my country - just that I really hate that song, and how it was shoved down our throats for a few years, but I don't know if it's the "worst song".
When I think of it, I'll post again.