Re: How do you stop this VERY FAT and TALL guy DOMINATING in streetball?
Many things you can try.
You can front him if a teammate has your back. You can double him with a quick guard, force him to pass it out. You can "pull the chair" from him if he's backing you in (in a game with actual refs you could also try to take a charge). If you pull this one off and he stumbles and falls you'll get a major victory. You can even attempt a hard foul coupled with some trash talking/psychological warfare. And of course, run as much as you can on offense, make him run after you.
You're not going to "stop" him if you don't have the weapons, but you can certainly frustrate him and reduce his ability to dominate.