A word that sounds worse than it is

Molestar

moh-les-TAR — To bother / annoy — not the crime "molest" implies in English

"¿Te molesta si abro la ventana?"
Do you mind if I open the window? (lit. does it bother you)

This one causes genuine alarm for English speakers the first time they hear it — in Spanish it's a completely mild, everyday verb for "to bother/annoy."

"The reaction the first time a student hears this word is priceless — I have to jump in fast to explain."— Graciela