Wangst is angst, but taken too far. It is similar to urple in that it is overblown and needlessly melodramatic. The word itself is a portmanteau of 'Wank' and 'Angst'. It is defined by the Pottersues FAQ as "like angst, only more self-congratulatory. It's the 'I hate being a princess, nobody understands how heavy all these pretty dresses and jewels are, and I'm allergic to my pony!' kind of angst".
It can also be called 'fanwank'.
'Wangst is masturbatory angst - the only one it pleases is yourself and no-one else gets any pleasure from it.' - Anonymous