A guy in my group started suggesting that things are better when me or others he doesn't like aren't around. It was fun at first, but he keeps pushing it... how can I stop this?

The reason I ask is because it's obvious he has it out for me and others. After a while it becomes uncomfortable and frustrating because it's like he enjoys criticizing everyone instead of chilling and having fun.

And he always targets either me or a couple of people that have one thing in common: we ignore him when he acts out. The problem is he is friendly and cool when we are not around, and a condescending-aggressive pain in the ass when we are there and he always ends up framing it like we are the problem, even though no one ever told him anything to make him trigger.

What's the deal with someone like this? Why does he have to be so competitive in the social group?