It happened when I was in high school. At that time, I kept getting invites to play chess from my classmate.
The chess game was included in the messenger app. I couldn't just block and ignore him. He already helped me a lot in studies via this app. Whenever I had problems, I just sent him the question and he'd explain it in some easy-to-understand way.
I knew my friend was good at chess. While I was terrible at it—he wouldn't know. It's not my thing, but I hate getting bullied from losing over and over.
So, the moment I accepted his invite. I opened another chess app and set the opponent's difficulty to max level.
Since my friend started as white, I also picked white for the other game, and I copied his moves.
When the grandmaster-level AI made their move, I mirrored the moves while facing my friend.
...as the result, he lost over and over.
We didn't chat again for the remainder of the night, but man, I was laughing so hard the entire time.
The next day, my friend immediately lashed out.
"Goddamn it! Why are you this good all along? Give me a break!"
Seeing him taking it seriously, my mind was filled with guilt—so yeah, I told him the truth.
"What the hell, man? That's basically cheating!"
"It's not cheating." I said, while putting a smug face, "I'm just playing it clever."
It made him facepalm, but I wasn't done yet.
"Even if I'm not good, it's not like you'll have mercy. You think it's fun? I don't."
At first, I thought he'll throw a tantrum, but no...he brushed it off like a trivial matter, fortunately.
...and our days went by like usual.
The best part--he never annoyed me with chess invites again.
now that's a nice friend