One of the bigger communist instances, like Lemmygrad.

They are infamous half because they are a big instance with a shared fringe worldview that is anathems to liberal democracy, so when something pops up in their feed, cultures clash.

The other half is that at least some of their users do like to use alts to "agitate" which is mostly trolling.

Just remember youll only get one side of the story since most big instances blacklisted them.

Pretty much but they claim to be 'communists' (though realistically they solely support the Chinese and Russian governments and never actually discuss communism as an economic policy) and isolated themselves from the rest of the fediverse for years. Last year they finally federated with everyone and were quickly defederated by most large instances because they're absolutely insufferable trolls who do nothing but fling feces and brigade in every post.