By cruelty I mean non "by the book" game design.
I am not even talking about unfair challenge, where a spike appears under your legs, where you have no way to tell it will before you visit that specific spot.
I am talking about things like… you reach a very difficult boss, but if you die, your last save point is very far behind.
So every time you die, you have to restart the difficult level again from the begining.
Perma death can be an example of cruelty, especially if the game is hard.
It can be the exact same game, one with perma death, and one with save anywhere… and the first will be more cruel than the latter.
Another example is putting difficult bits right from the start of the game.
So what I mean by cruel, is the game developer insisting on putting either very difficult bits, or very long chore before a difficult bit.
Generally the pace and intensity of the difficult part, are much higher.
So like… one could say “Why would I need to do the same level twice only to reach the same boss I failed?”
But another player might like the “classic”, where the boss would be more rewarding to defeat, because every attempt requires a “chore” to get to the boss.
The best example is a level before a boss.
Do you have a save point right before the boss? So you have as many attempts as you want, just for the boss bit?
Or do you have to complete a level(chore) for every attempt to fight the boss?
Will the latter make the boss fight more rewarding psychologically?