Yes.have you encountered a really bad DM ?
In one case, was determined to have the adventure proceed as per the scripted module, and so failed to play NPCs honestly (a captured kobold) in order to avoid giving the players the information they wanted (we, as our PCs, were seeking information from the kobold about how it had entered the city, what the disposition of kobold forces was, etc) so as to prevent the players declaring actions for their PCs that would disrupt the script (we wanted to learn where the kobolds were so we could take the fight to them).What did he do ?
In another case, was determined to have the twist he'd scripted play out, and so had a NPC betray us with no real warning, and in a way that was unavoidable given that the only option for play that had been presented to us by the GM was going on the NPC's mission. So our reward for doing as the GM told us to do was to be made to look like schmucks.
In a third case, had lost control of the fiction due to we, the players, building an elaborate set of relationships among our PCs and between our PCs and various elements of the setting; and so teleported us all 100 years into the future, killing off all the fiction what we'd created and starting with a blank slate where only he had any knowledge or control.
I don't know about damage, but in each case the game ended. In the first we staged a player revolt and started a new game. As a courtesy we invited the GM to join as a player, but he declined. In the second case, the game fizzled out after a handful of sessions. In the third case, I left the campaign not long after and heard that it had come to an end a few sessions after I left.What kind of damage did he cause and why ?
There's no reason why RPGers should put up with crappy GMing.