Hello, I’m not sure if this question interests you, but it interests me.

Based on your experience, what are the most toxic communities in the world of competitive programming and the most helpful communities, from when you were a beginner to when you became good at it?

For me the answer is Codeforces as one of the most toxic communities especially for beginners and atcoder as the most helpful one. (I hope nobody take it personally but that's My opinion).