The one thing that I've seen that can make a player change is if they join a pre-existing group that already has a strong "group culture." At that point, peer pressure can lead to a degree of self-restraint, which eventually solidifies into lasting change. That said, this usually happens immediately, or not at all, and requires that the one player be heavily outnumbered.
Maze is also right though -- there's always potential for growth, if not rapid change, but this is usually a very slow process.
As much as we as gamers talk about the GM setting the tone for a session, campaign, group, etc -- I've always found that there's a very powerful "group culture" thing that goes on, regardless of who is actually GMing. Has anyone else experienced this?
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