One from Norway:
Back in 2002 20-year-old Azar Karadas made the move from Brann to Rosenborg, two teams that had developed a particularly fierce rivalry during the 90s. Traditionally Rosenborg, hailing from Trondheim, had mostly been the rivals of Molde, due to the proximity of the clubs, and Bodø/Glimt, the closest other top team from "The North", but the games between the Bergen-based Brann and Rosenborg were arguably even more heated at the time, possibly due to the fact that people from Bergen and Trondheim are slightly more passionate about football than the average Norwegian. Only the Vålerenga/Lillestrøm derby in Oslo really comes close in terms of passion. Of course, nothing in Norway has ever come close to comparing to the most fervent European Ultras, so while I use terms like 'fierce' and 'passionate', we're still not in frothing-at-the-mouth territory by any means. The extent of our rivalries mostly involves calling opposition fans farmers and singing songs with low-quality rhymes about how awesome our team is and how shite everyone else is. "We are cool, we are smart. Go Start!" That sort of thing. The transfer of Azar Karadas probably displayed the worst of the worst of what we have to offer.
What happened, you might ask? Well, he was called Judas for starters. Obviously, right? That's Scorned Fan 101. Happens everywhere. In addition to that he received threatening notes in his mailbox in Bergen, saying "Never show your face here again!", and some genius also wrote "You're going to die!" in the snow in front of his apartment... in ketchup.
Karadas eventually left Rosenborg and spent a few seasons abroad, before returning home to Brann in 2007. Brann won the league title the same year, for the first time in decades, and they haven't won it since. If the animosity towards Karadas was a thing when he returned it was definitely forgotten by the end of the year. A banner was flown at the stands that read "We hated you so much because we loved you so dearly". Aww.
I guess we're not quite the ferocious raping and plundering Vikings we used to be.