Speaking of the "red-headed stepchild of Europe", I was watching a video on YouTube called "Serbia's Secret War". From that video, I could list controversies that may or may not be known:
1) Despite suffering a lot from atrocities committed against its people during WWII, Serbia was actually more efficient in taking part in the Holocaust (under the Nedic government, that is) than Croatia, to the point where the Nazis declared Serbia to be the first nation in Nazi Occupied Europe to be Judenfrei.
2) The Serbs had their own controversial religious figure that acted as a de facto mirror to Cardinal Aloysius Stepinac in Nikolaj Velimirovic. Velimirovic had also expressed his own brand of anti-Semitism, while being locked up under house arrest in Dachau, and he's also canonized as a saint in 2003.
3) The Chetniks pretty much collaborated with any faction, as long as they can come out on top. Whether it was the Germans, or even the Partisans, they wanted to benefit from any kind of collaboration as long as they can benefit from it.