I suspect all of their rulings came from them. I suspect no DM ever allowed the stuff he thought he could do.Most of this seemed to stem from having a Rule of Cool DM who decided that if you're using psychic effects cast from stealth, enemies don't even get to roll initiative, because they're not aware at all that they're under attack. This gave him an incredibly exaggerated understanding of how powerful stealth is.
But ... they can't even defend themselves and it's likely they're just an unstable individual. For me it's not fair to continue the trash talk.
Suffice to say, even with powerful builds, no single build IMHO will ever be able to take over the world. In a 1-on-1 fight between 20th level PCs it's going to depend as much, if not more, on luck, tactics and specifics of the scenario.