So I just finished up Medal of Honor: Allied Assault on Hard, just the base game not the expansions, and the last few levels are some deep bull. While the rest of the game was merely hard enough to F5 through, at some point I just said screw it and cheated just to get through the remaining levels. To start off, you're supposed to not only survive a sniper gauntlet, but protect dudes from getting picked off. Solution? Noclip up to the guard towers and snipe everyone in god mode. The next few levels are somewhat reasonable although the AI blind firing with perfect accuracy before you can even see them is... uh, not fun, especially when you can't hit them from the same angle. Having to reload constantly and crawl through every encounter and quick saving every few steps. And to top it off, the last level is everything exploding on top of you with enemies pouring out in a tidal wave of hitscan hell and snipers. Fuck you game, god mode on. I'll be sure to simply play on Normal in the expansions when I get to them if it's anything like the base game where the latter half of the game is a bunch of sniper alleys.

What are some games where the hard mode is not only infuriating, but the only way to get through it is sheer attrition if not outright cheating?

God of War (2018) on Give Me God of War difficulty. The damage multipliers are completely skewed to the enemy. Even easy enemies can kill you in a few hits, and they all feel bullet spongey.

Most games, even those from over a decade ago allow you to change the difficulty during the game. If it is too hard, just play on an easier difficulty?

Everyone has different expectations of game difficulty, and different skill levels. I'm sure if you searched for videos online, you'd see people playing through the section you had trouble with on even harder difficulty than you.

One game that really gave me trouble was the end of Vampire the Masquerade: Bloodlines. I was enjoying the story, but then that end was basically just a brick wall even at the easiest difficulty. So I just played the rest of it with God Mode on. But I recognise that other people more skilled than me probably didn't have as much trouble. Each person has a different point at which they're no longer having fun.

That sniper level was indeed "memorable"... :-) I remember "Mental" mode in Serious Sam FE being challenging because it's Hard Mode + it causes the enemies to fade in and out of view / become semi-invisible half the time. Given how fast the gameplay is, if one approaches you from behind and you turn and don't see it (whilst invisible), you've got no chance.

Personally though I usually just play on Medium unless the game does something more intelligent (eg, better AI) on harder modes beyond just ramping up enemy HP's to the point of turning gameplay into a "peashooter vs tank" grind-fest. Doom (1993) got so much of this right. Harder = increased enemy count + reduced ammo = If you wanted to clear the level (100% enemies) it forced you to play differently if you couldn't use the more powerful weapons as much. In fact there were some WAD's where there's (deliberately) less total ammo than total enemy HP's which forced you to get creative in 'playing' different monster types off each other, lure them into crushers, etc. Amazes me how a 30 year old FPS can still feel "smarter" in terms of upping the challenge without cheap hitpoint grind vs much newer games.

Devil May Cry has a difficulty mode named Hell and Hell in a few titles of the series.
Enemies are more aggressive, have more health or rather you only deal 75% or 85% of your damage and you die in one hit. You have a couple resurrection items per level though, it's either 2 or 3.

10 years ago I was able to beat the hardest difficulty modes of DMC 3 and 4 (including the 1 hit KO mode), nowadays I'm having a hard time beating hard mode while using cheese strategies. :D

Edit: Not that you'd need to play the Hell and Hell mode, most people will never finish the hard mode Dante Must Die as you die (depending on the enemy type) within 3 to 6 hits. It's frustrating at times. :P

Some games like Alan Wake have certain content limited to the hardest game mode.

Anyway, I am not as fast as I used to be. While I still have no problems with Ego shooters and such, certain 2D side scrollers give me a harder time than they used to.
Edit: Most Ego Shooters, not ones like Doom Eternal, where you get put in a Arena with hordes of monsters, that's just not my thing.

HZD on ultra hard was quite a challenge. Lately I started Marvel's Spider-man on hardest difficulty and so far it's doable for me. I guess once everything starts exploding I'll be out of my league. That was already a pita on normal mode in Spider-man Miles Morales. I could higher combo achievements once the enemies all got rocket launchers and similar stuff.
On the next playthrough I have to get these as early as possible.

My answer: when you don't have fun anymore but for some reason you don't want to simply quit the game.

It's funny because I did the same you did in Allied Assault, the later levels especially in the Italian campaign are absolutely BS.

Terror from the deep!
Superhuman difficulty level!
I'm not sure if it was me or if it was a bug in my version or whatever but the AI could see you behind walls and then possess your units, on top of the way-off- the-chart hit points of enemies.
Basically is normal to get a fully geared squad literally slaughtered in a few turns AND at some point UFO's activity increases dramatically, corruption ramps up, terror sites become more frequent, alien bases crop up like mushrooms.
A nightmare.
I usually go for the hardest mode regardless but that felt way, way too unreasonable and unfair.
I closed the game and left it there 30 years ago I believe, those memories still haunt my nights.

I think that games should be played as the developers intended them to unless it is unfair to the gamer or, conversely, if there are mechanics or features that I consider cheats, like, wallhack, third personing abuse, GPS abuse. which are kind of commonly accepted since basically the 2000s, I believe.

Allied Assault on hard is one of my favorite FPS games to play through. The ruined city full of snipers is actually the main highlight of my every playthrough. No damn lasers instantly telling you where they are. No 2 second protection before they start firing at you and you have to actually locate them yourself based on where you are getting shot from. I honestly hate how enemy snipers are done in pretty much every modern FPS game. Along with the overall aversion to hitscan enemies. I found it much easier than Serious simply off of the fact that Mental is based on Hard. The enemies fading in and out is not really that bad as it seems and enemies dealing 25% less damage than on Serious is a much larger benefit than the fading out is a detriment. You still also have sound cues, which are often much more important than actually seeing the enemy (Kamikaze scream, Kleer hoof clapping, Werebull stomping/roars etc.). Kleers and Kamikazes also barely ever sidestep your aim on Mental, compared to Serious. But I've played hundreds of hours of Serious Sams :P A decade ago, maybe. But in older games, it was basically never an option.

What Enebias said. In single player, it's completely up to you whether you cheat or not, you don't need to justify it, but I understand that it might feel wrong, like an admission of failure, and ruin part of the fun. However, the game had already lost you at that point, you weren't enjoying it anymore anyway, so the alternatives would have been to abandon it for good and never see the end of it, or to torment yourself endlessly for no good reason. Since you were close to the end, I can totally relate to wanting some closure and seeing it through to the end, even with a little help.

Personally, I never play on Hard, in order to avoid such situations. Granted, many games tend to be on the easy side on Normal difficulty, but since I can't know how hard Hard Mode really is before I play it, I still prefer the game to be a little easier over having frustrating experiences like yours.

Try X-Wing (1993). It doesn't even have difficulty settings but some missions are next to impossible. X-Wing CD made it a bit better by changing a couple of the missions, but it's still almost impossible.

And on topic, I pick the difficulty where the game will offer at least some challenge. Which usually means the hardest or close to it in most games. This is of course subjective, but I find the normal difficulty in most games simply boring and I enjoy them much less if I can just roflstomp through them without resistance.

Cheats I use only when messing around, never on the first playthrough. Occasionally, I use them to get around some gamebreaking bugs (like noclip), but that's it.

I don't really like bending the rules of games. I guess you could say I'm a purist in the sense that I like to experience the game the way the game creator's intended it.

If it gets really frustrating to the point where I want to stop playing, because I'm feeling like I'm wasting my time:
- If I enjoyed the game up to that point, I'll look for a guide online
- If not, I'll just stop playing right there

If a guide can't help me, then I'll stop playing the game either way (if I use cheats, I'll feel like I stopped playing the game the moment I started using them anyways).

If the game had a story and I really want to know what happens, I'll look online for that (preferably some youtube video, but a forum thread or wiki will do the trick in a crunch).

The final dungeon of Elminage Gothic. Though I didn't cheat I just dropped the game.

i didn't find the final dungeon to be that bad.

On the other hand, the final post-game dungeon did make me quit after a while, but by that point I had already gotten more than my money's worth of the game.

In fact, I feel like I may replay that game at some point. (Plan is to including a brawler in my party, perhaps a faerie brawler, a build that actually looks like it could work.)

As for "unreasonable enough to cheat", I would say when the game is being not just hard, but unforgiving, and hard in the wrong way. For example:
* If the game randomly kills you, taking you back to the last save point, that might be a time to cheat.
* If the game randomly deletes your characters, then it is definitely time to cheat, or at least find ways to copy the save file to protect it from the game. (Wizardry games will, in certain circumstances, randomly delete your characters, and it's not a bug. Fortunately, this doesn't happen in Wizardry 6-8 (or in Wizardry 4, for that matter).
* In Might & Magic 2, the penalty for stealing Murray's treasure, if you save before realizing what happened, might drive one to cheat.

There's also another reason to cheat: To get an interesting gameplay experience that's unlikely to come up normally. For example, going back to Wizardry, hex editing a new character's class to Lord or Ninja would qualify. (I suggest creating the character as a Fighter for Lord, or a Thief for Ninja, as that will likely give you an appropriate amount of starting HP and no spells you shouldn't have.)

Also, worth noting that I don't consider looking things on the internet to be cheating, and I typically don't count glitch exploits as cheating, either.