it's a much more subjective category, the shitty trip to somewhere
I've actually known people not like Barry Island, which is frankly bizarre and a sign of mental illness, but equally a town is at the mercy of the people you meet and the mood you are in
Somebody in the positive 3 places named Bristol as a good place, my initial experiences of the first few trips to Bristol were awful. It literally stank and the people were aggressive. They had a zoo you needed a mortgage to enter and half the roads had road works that had no diversion signage. But since then I've been to other areas and I've really enjoyed the vibe.
Similarly, Paris is fantastic but I know so many people that swear they would never ever go back. So with that caveat in mind, my 3 piss poor places are:
1. Edinburgh, dull, damp, boring, expensive.
2. Dublin, just didn't get into the spirit of it I guess, it was just a slightly run down working city. Perhaps I needed a local guide or more time or a different attitude on the day.
3. Mombasa, truly third world, but with hired thugs to keep the poor away from the tourists' dollars.