The leaked document of Facebook's "Dangerous Individuals and Organizations List" includes several antifa groups active on Twitter. Facebook calls them each an "armed militia group." https://theintercept.com/document/2021/10/12/facebook-dangerous-individuals-and-organizations-list-reproduced-snapshot/

@PNWYLF (riot organizer)
@crimethinc (crime guides)
@PugetSoundJBGC (gun militia)