Like I said, I feel your difficulty will be the difference between what *you* think "sounds bad" and what the computer can detect to be a bad mp3. The encoding of the song could be perfect; perfectly encoded skips, perfectly encoded silences, perfectly encoded clicks. If most of the bad ones are short, could you put them all in one folder and sort them by size? Then you can start listening to them at the small end of the list, deleting the ones which are damaged, and when you start getting tracks which are all mostly okay, then you can stop checking them. Obviously, if you then find a broken one while shuffling through then you can delete that one manually.

But, if you're looking for more methods, you could do worse than this