At one point my dad taught me chess, and within a few weeks I could beat him because he was never very good.

Years later, I started playing my stepdad, with an 1800 rating who ran tournaments of blitz chess every day at his workplace. I had learned to play better at my chess club at school, and knew how to play speed chess, and was even beating most of the club at school. But this guy never, ever gave an inch on chess. If you made the exact same mistake twice in two games, you just got punished the exact same way in two consecutive games. He probably would have helped me if I'd asked, but I was too stubborn for that. We bought a chess clock so we could play at home, and played every night. I think we halfway wore out the first chess clock before I ever beat him once. He was momentarily annoyed and then quietly beaming the rest of the night. I was too shocked to say anything except good game.