game What is the most unfair mechanic you have learned to love?

[Alamson]

Sometimes the way a game works when we interact with it leaves much to be desired. We feel short-changed or sad but there is nothing we can do other than to take the game as it is. "Permadeath" is an example; you can never use a character again once it is killed. You may have to use a new character or restart the game. Players usually don't like this but that is how the game is designed.
What is yours? Is it insta kill spike or RNG curse? Share your thoughts.