One of the favorite pretexts for war and violence in the world is religious differences. Religion has long been a primary organizing principle of societies, so it's hardly surprising that competing groups often come to violence and minorities are a favorite target when things go awry. It seems that the United States has a Commission on International Religious Freedom. Of course it's an American Commission, appointed by American politicians, so its hardly a completely unbiased source. The members, with a few exceptions, have typically European Christian or Jewish names. They do seem to take their job seriously, however, and their reports present plenty of examples.
Offending nations are classified by Tier (Tier one is worst) and whether the Tier is merely recommended or sanctioned by State Department designation. One might not be surprised to find that Tier 1 is dominated by the officially Communist states (China, Vietnam, and North Korea) and numerous Islamic states. Many of these states are officially intolerant.
Tier 2 includes the major states of India, Indonesia, and Russia. A large proportion of the world's population lives in the 33 monitored countries. Cuba is the only American country to make the list, and the European nations are mostly ex-Communist. There are countries that might qualify that don't make the list, for example Israel. Perpetrators include Communist governments, Muslims, Hindus, Christians and Buddhists (at least) and the victims list includes most or all of the above but is far longer, though in many cases perpetrators and victims cannot be clearly sorted.
Communist persecution obviously has declined with the collapse of Communism, but Islamic and Hindu fundamentalists/nationalists (among others) have jumped into the breach.
The worst violation of religious freedom is religious war, but that, at present, seems largely concentrated between Islamic groups and almost everybody else, including each other.