How are we defining supremacy groups? Strictly racial? I would argue extreme environmentalists being supremacy groups when they do things like slash the tires of SUVs. They truly think they are morally superior and everyone who is not like them is trash. Also, extreme animal rights activists and extreme LGBT activists who argue they are superior.
In recent years, these victim based supremacy groups have been worse than traditional white supremacists. White supremacists, while being scummy people, are so marginalized that only a very small percentage of the population takes them seriously. Black supremacists can be openly racist and have the support of the media. Some black supremacists will argue it is impossible for them to be racists because racism requires power and only white people have power and then they will explicitly denounce all white people. They will make statements that everyone would agree was racist if it were a white person saying it about a black person. They will openly argue for segregationist policies that exclude whites from public spaces and only receive minimal criminals. They will argue for racial quotas and racially discriminatory hiring practices and admission policies and they will actually receive praise under the banner of promoting diversity.
White supremacists have historically been awful, but today are viewed as trash by almost everyone. These victim based supremacy groups are a much bigger problem in terms of level of influence and the lack of push back they receive.