I tell people what I think of them... within appropriate context, and when being an adult (polite) doesn’t apply.
I’m a bit of a dick and will talk to other people about someone pissing me off though, simply because it would be inappropriate to say as much to the actual person (like people are entitled to have individual personalities, quirks, biases, ignorances, make mistakes, have blind sides.... doesn’t mean it isn’t annoying tho), but I also want to vent to someone who would hopefully feel the same way/understand.
I’ve since learnt I have a much lower threshold for what annoys me about people than most others so I come across as just a plain bitch!
...People like me piss me off.