Like who? In North America, I haven't seen any evidence of this. The example that's always posted, including in this thread, is a lone actor that hit a few people with a bike lock years ago.
According to the Government Accountability Office of the United States, 73% of violent extremist incidents that resulted in deaths since September 12, 2001 were caused by right-wing extremist groups. That's not even including what they label as Islamist extremists and "incel" extremists which both could also easily be classified as right-wing extremism. In North America, violent left-wing extremism is barely a blip on the radar and yet we keep hearing "conservative" talking heads go on about Antifa. It seems like little more than a politically motivated distraction much like Obamagate.