Definitely not the "worst" band ever, but Pearl Jam is definitely one of my least liked bands. Really I love Black and a few other things are cool/ok but everything else I've heard is awful. Eddie Vedder is definitely one of the most grating vocalists and very overrated.
There are definitely bands worse than Pearl Jam. But when I think of my least liked bands that had music forced into my ears by radio stations and friends/family, Pearl Jam tops that list.