Ahem.
The fact that some GMs think they are all powerful and can do anything they want when they feel like it in an RP. I understand some people like to take their roleplays seriously and such and all that, but if someone criticizes the way you are handling things... and the GM seemingly nerfs your character or gets your character to have something horrible happen to them, because of 'plot', the very next day. It tends ro grind my gears til sparks are flying.
I don't know the context, but GMs are the directors of the RP and kinda are “all powerful”. Doesn't mean they should be assholes or unflinching tyrants, but they do have that autonomy and that right to do what they think is best for their RP.