The reputation of Hull is marred by an abnormally large representation of drug addicts, thieves, and violent criminals. Its drug, theft, and assault problem that shows up quite clearly in the National Statistics.
Superficially, Hull city centre is quite nice, but you don't have to walk for very long to see the sudden and sharp drop in wealth - it is a city that demonstrates vast wealth inequality per kilometre travelled - even more than many areas of London, Paris, or Berlin, IMO.
However, I've stayed in Hull for a week and didn't feel like it was that bad. It's basically just poor and most of the problems are vandalism from kids with nothing else to do and druggies/alcoholics looking for another score. Take my report with a pinch of salt too, since it's over a decade out of date at this point and a lot can change in a decade....