Muramasa, a 2009 game for the Wii developed by Vanillaware, is for my tastes, too easy on easy and too hard on hard. But on Shigurui (lit. “Death Frenzy”) its ultimate difficulty, in which you die instantly after being hit, is to me perfect, and paradoxically, easier and less frustrating than hard mode.
One hit death is not actually as scary as it sounds; in Muramasa, it's possible to block every single attack in the game (with few, avoidable exceptions) simply by holding down the attack button. Instead, the health of one's sword is decreased, and one can and must rapidly switch between a set of three equipped swords in order to continue blocking. There is no way to instantly die; all attacks are avoidable or blockable.
In other modes, having an HP bar essentially boils down to how many unblocked attacks are allowed before restarting. On paper, it doesn’t seem possible how forgoing this allowance might make the game easier. But because Shigurui mode makes the margin for error impossible, it stops teaching and encouraging and rewarding reckless behavior that will, over time, make the experience more frustrating with seemingly random deaths.
Normally, a misstep means a loss of health, which is not as bad as dying; however, having that buffer means that letting down one's guard for risky behavior, which I often do (as I love dying pointlessly trying to secure a kill, because I never learn) and occasionally the reward appears to be worth the lost health. But over time it isn’t. So an outright death means being forced to play the correct way, which is actually quite easy once you get the hang of it. It’s just that it’s easier to get the hang of it when you’re blocking all the time, instead of being sloppy with it.
Shigurui mode makes reckless play impossible, and it encourages a more precise and disciplined style that is more fun to maintain and less frustrating to fail, in part due to Muramasa’s frequent checkpoints and quick restarts. I think hard mode would be actually be easier, but only if I was a better player—Shigurui mode, however, teaches me how to play better.
Ultimately, I think that difficulty may be a concept that isn’t actually beneficial to players. What is more important than difficulty is accessability—the question of whether or not new players can pick up the game—and I believe the most effective way to broach this is to be better at teaching players how to play, rather than giving them a half-formed game. I have beaten games on easy mode before while barely understanding how I was doing it. Easy modes seem pointless and patronizing if they aren’t willing to allow players to experience what the game has to offer.