Covering the facetious and serious sides of the question:

Hearing someone slaughter a song that is precious to you.

Any song that has ear worm potential played repeatedly till it wears a groove in your brain.

Too much too loud anything- gets to the physically painful point. Experienced this ONCE: National Lampoon's road show spoofing Woodstock, "Lemmings" ended with the Pink Floyd-like band cranking up the volume till the audience started leaving in droves. The vibration made your insides rattle, and empty chairs moved across the floor. Painful gimmick.

Something with a catchy tune that makes you want to sing along that has horrid lyrics you wouldn't utter unless subjected to some physical torture.

I'm with Senoufou on torture being wrong as well as ineffective, and truly don't like the idea of any music, however bad, out of tune, or inane it might be, used as a weapon against someone.

Joanne, who has already exceeded her lifetime allotment of "MacArthur Park"