North Dakota and Wyoming. North Dakota hockey (the former Sioux, not the NDSU Bison) and Wyoming have very similar fan bases in terms of demographics, though North Dakota has championships to back up their talk. I've never seen such poor losers and poor winners as North Dakota--basically image the Wyoming fanbase but with an Oklahoma or Florida State caliber team to root for.

Ohio State and Michigan. Both fanbases are so annoying to anyone living in Big Ten country, it's hard to figure out which fanbase worse.

Mexico. Agree with RSLCoug. While the average El Tri fan seems fine on an individual basis, this fanbase has so many bad eggs doing some nasty stuff (bags of urine, batteries, etc.) that they make any fanbases on this list look like amateurs.

While fans of my rival schools Utah, Wisconsin, and Iowa have their bag eggs too, their bad eggs aren't numerous enough or nasty enough to lower the overall level of these fanbases to make my list.