Newcastle, Aston Villa and Leeds all fit the bill here. Possibly in their recent history Everton too
France - Marseille have always been a very up and down and inconsistent team in recent times given the size of the city and their stadium. Another name is Bordeaux, they should be threatening to finish in a Champions League spot every season imo. Especially when you consider they are based in one of France's biggest cities, have a large stadium capacity and also have a large catchment area with no other major competing club within 50/60 miles of them.
Any others i have missed out from above?
I didn't find the right solution from the Internet.
References:http://www.footballforums.net/threads/european-footballs-most-underachieving-clubs.263381/