I was involved for a couple months with a National Labor Federation group. Each branch calls themselves something different. Luckily I googled them and got myself and a friend out before we were fully dragged in. Just google any group you’re interested in to see if others are accusing them of being a cult.

Where I live, the socialist alternative aka SALT. They’re rather abusive towards their members and are pretty broadly hated by every other group because they co-opt movements and turn any rally into a chance to sell things and make a profit. They’re well known for being very manipulative and forceful with university students in particular. I’ve heard nothing but disgusting stories from the people who got out.