IMO, the worst community i've known so far is a community from a small game called GROWTOPIA.
It used to be fun, i've made a lot of friends from it. But this past few years, the game has gone downhill. To the point that it become one of the most capitalistic MMO game out there. The main motivation for people to play that game is to own as much pixel currency as they can. People scamming each other, price manipulation, auto clicker, market manipulation. even it's a normal sight to see friend backstabing each other.
Going anywhere in that game is a complete nightmare as you'll mostly see people bragging about their pixel wealth. People bragging about how much time they have wasted just to become richer in a game that will going to die in a few years, people whining, crying, ranting, people who alwasy ask for a donation ell, etc.
If you wish to improve your anger control. I suggest playing that game. Since you'll be frustated every single time you play that game.