AntifaWatch has compiled a massive database of people arrested for left-wing violence, as well as people who have self-identified as members of violent left-wing groups. The website is incredibly searchable and even has a built in facial recognition feature.
We tested the facial recognition using a well known Antifa leader who has been arrested in multiple US states. It worked!
There are currently over 5,000 entries. This is a massive resource to monitor and study left-wing extremism, yet few people know of its existence.