A so-so contest & a nice enough blog ... but not the real thing either. First of all, there should be a category "ugly sans plus" (viz. standalone), and a second category "ugly and ill advised in that context" (viz. ruining its surroundings). For the latter category, I think Belgium will be hard to beat ... Just check Brussels' blandest Tour Blaton for an excellent example of the planner's dream going wrong. Especially since it was built upon the ruins of Victor Horta's Maison du Peuple (how brutal can you get). Apart from the aforementioned categories, I'd go for extra listings such as "ugly, pompous and expensive" (viz. corporate) vs. "ugly and desperate" (viz. a hapless citizen's home) as well.
http://denis47.canalblog.com/archives/2011/03/01/20512632.html  [source of image #1]
http://www.skyscrapercity.com/showthread.php?t=675018&page=4  [source of image #2]
http://www.skyscrapercity.com/archive/index.php/t-320054.html
http://www.virtualtourist.com/press-center/ugliest-buildings-list
http://www.tbx.be/fr/AvantApres/list/app.rvb
http://uglybelgianhouses.tumblr.com/
http://www.bruxellisation.com/