There is a tie in this contest for me:
Livingstone, total shithole especially the west side around the bus depot and it's impossible to walk to anywhere.
Paisley, inhabited by schemies, neds, hoodies and scroungers the place feels like an eastern-european third world country, the locals would steal your shite if you did not flush it away, never go there with any valuables, dress down, dress like a tramp, blend in.