Hey /tg/. I'm GMing my first campaign, a homebrew alternate history weird western using modified Shadowrun rules. So far, everybody in the group I game with has loved it, to the point that the GM of the game we've been playing is considering ending his game, so we can play the game I'm running more than once every two weeks.
However, the GM also tends to be 'that guy' when he isn't running a game. When i first told him I was going to be running some sort of game, he told me he would make a high charisma based character and "fuck your setting into the dirt".
And so, when I started with a two player one-off game, my first time running a game ever, he made a character with charisma skills so high, he was able to hit his charisma limit, and tried insisting that meant his character got what he wanted.
At first I tolerated it, since it was mildly amusing - He conviced the other player that the job of robbing a train wasn't good enough, and ended up managing to blow up the railroad just before the train went over a gorge. While that did fuck up the setting, it also allowed me to diverge from real history in a way I wanted to. However, he didn't stop there, and he began to take over the town I had set the game in (Laramie), insisting that since he had rolled his limit, and his limit was higher than the average dicepool of the people in Laramie, that he would be able to convince them to sign over their buisnesses to him by using fancy words and talking around them in circles.
By the time I managed to put a stop to it, he had taken over 80% of the town, missing only the blacksmith (who he tried to seduce the wife of infront of him, and was chased off with a shotgun), and the bank (who was owned by a jewish guy, and refused to shake the native american snake oil salesman's hand, and thus avoided being pricked with a needle filled with some sort of drug.).
He said he's going to do it again when he joins the full game itself. How do I damage control a Charisma based 'that guy'?