He didn't even have the 'common courtesy' [=he was not even as polite as people can usually be expected to be] to say goodbye when he left.
He picked up the airport 'courtesy phone' [=a telephone that customers can use to call the company that provides it] to call for a car.
They paid a 'courtesy call' on the ambassador. [=they visited the ambassador because it was the polite thing to do]
(..) could end your friend's life in an instant. I gotta tell you, he's not really my friend. Saving his life is more of a professional courtesy. You've saved nothing. Your powers are inconsequential compared to mine. Yeah, but the kid's (..)2018 Avengers: Infinity War