Lots of people saying "report him," and in an ideal world, that would work. In my experience, it's more more likely they know the guy, he does this regularly to 'thin the herd' or whatever, and the gym staff won't do a damn thing.

In my case, it was one of their personal trainers who harassed me every time I went in until I couldn't stand to show my face in the gym anymore. We had signed a contract for a full year, and lasted two months due to this guy's bullying, so there was a clear financial gain for them in having us pay and not show our fat faces in their pretty gym.

Think about the money you are spending on your membership. Would it be possible to spend that much each month on equipment for your garage or spare room setting up a home gym? That's what we did, and haven't looked back once.

Gyms are horribly toxic environments unless you are already in pretty good shape at the start.