Maybe this has been asked a million times (I didn't find it... links and useful search queries are appreciated). But how should I deal with a toxic friend in a group?

I'm sure this situation is very common.

More details below, you could just skip it :) ==========

We are a large group 7-11 friends ages 20-30 (group A). The group is very nice, and I am the common friend with all of them. After the summer the group will be 5-7 friends (the others return home after 6 months), with the toxic friend and his girlfriend in the group. The rest of the friends were friends for longer.

The toxic is very subtle. I know him for 8+ years, I didn't like him at first but I don't remember why. Recently I have seen his subtle manipulative behavior with another circle of people (group B), somewhat larger and "less friends". He took the lead a long time ago, decreased meeting frequency by a lot.

[Edit: This paragraph is hard to understand, try to improve it] This is an unsorted list of things (very broad) that I recently noticed:

• He is blaming others for things not going well.
• He blames other people for his own actions.
• Instead of working as a group, he works only with a friend and he does not report any kind of progress, we are "guilty" for not taking initiative.
• When a task has to be done, he asks very open-ended questions that nobody can answer in the chat. One of the persons that could have answered was outside the group because she was his ex and he didn't want to be in the chat with her. We had to forward messages back and forth between them, communication was a big issue, we hardly met in person this year. Then he blames that nobody answers his questions.

We said everything in the previous paragraph to him, we are "personally attacking him". The person that he blames the most for things not going well is her ex. For rest of the group (except him and his friend), the bad atmosphere is his fault. We work well together, if someone doesn't have time to do something, someone else does it. We meet regularly, etc. From now on we will be taking the lead so hopefully thing will go better. (He resigned willingly, as everything is falling apart from his point of view).

The issue remains with my group of friends, I'm good friends with the others, but I don't want to find myself in shitty situations with them.

Some time ago, in a smaller group 3-5 friends (group C), ages 20-25 I detected toxic behavior with one of the friends (always wanted the group to follow his plans). I didn't know how to handle the situation, so I showed up less with them using working on (group B) as an excuse, as I didn't want him to feel bad. Just seeing the group less backfired with him being a very active member in group B just to keep the friendship with me.... Luckily he improved a lot recently, but we are still not so much friends as we once were.

Now talking about the toxic guy I'm currently asking: I thing he is not ok and I'm a bit worried. Maybe he needs help, and if something like this happened to me, it would feel very bad if friends just vanished.

There is a lot of advice in the line of "you are not responsible for others feelings" and to avoid toxic people, this is what I followed the first time that I found myself in this situation. I'm not sure anymore how to deal with this.

I've you have read so far, thank you a lot :)