I would nominate Stoke-on-Trent for ugliness. Strange place made up of 5 towns which doesn't gel into one city. It is named after Stoke but the town of Hanley is the commercial and main centre. Have been there twice and opinion never changed.
Yes, Brighton & Hove is a city made up of two towns but firstly Brighton is the first named and is accepted as the main centre. Also travelling between both is seamless.
Possibly the most grim, and most grimey, northern hellhole I have ever had the misfortune to visit on more than one occasion. If there are worse places I have yet to visit them, and if they are in existence they should be flattened, along with Stoke.