Dark souls, Bloodborne

EU4...

I like most other Paradox games and I'm at least decent in them I'd say but EU4 just eludes me.

The classic arcade game Venture. Go ahead, make my day:

https://archive.org/details/arcade_venture#

Venture is a 1981 arcade game by Exidy. The goal of Venture is to collect treasure from a dungeon. The player, named Winky, is equipped with a bow and arrow and explores a dungeon with rooms and hallways. The hallways are patrolled by large, tentacled monsters (the "Hallmonsters", according to Exidy) who cannot be injured, killed, or stopped in any way. Once in a room, the player may kill monsters, avoid traps and gather treasures. If they stay in any room too long, a Hallmonster will enter the room, chase and kill them. In this way, the Hallmonsters serve the same role as "Evil Otto" in the arcade game Berzerk. The more quickly the player finishes each level, the higher their score. The goal of each room is only to steal the room's treasure. In most rooms, it is possible (though difficult) to steal the treasure without defeating the monsters within. Some rooms have traps that are only sprung when the player picks up the treasure. For instance, in "The Two-Headed Room", two 2-headed ettins appears the moment the player picks up the prize. Players die if they touch a monster or the corpse of a monster. Dead monsters decay over time and their corpses may block room exits, delaying the player and possibly allowing the Hallmonster to enter. Shooting a corpse causes it to regress back to its initial death phase. The monsters themselves move in specific patterns but may deviate to chase the player, and the game's AI allows them to dodge the player's shots with varying degrees of "intelligence" (for example, the snakes of "The Serpent Room" are relatively slow to dodge arrows, the trolls of "The Troll Room" are quite adept at evasion). The game consists of three different dungeon levels with different rooms. After clearing all the rooms in a level the player advances to the next. After three levels the room pattern and monsters repeat, but at a higher speed and a different set of treasures.
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Released
1981

Ninja Garden 2 on Master Ninja mode. It's the hardest action game I've ever played. Non-stop Incendiary Shuriken ninjas, rockets, and mini bosses. You literally cannot stop moving, make any mistakes, and have to react in split seconds the entire time or you're dead. It's borderline impossible. Never again.

This is one is genre specific, but Caesar 3. I love city builders and have played them for as long as they've existed. I've learned all the little tricks and systems of the ones I've played, exploiting esoteric mechanics and optimizing my little utopias and creating epic, sprawling empires that far exceed every metric asked of me. That said, Caesar 3 is a challenge I still relish after (oh wow, has it really been) 25 years. It's the only city builder where the "peaceful" branch in the story is harder than the "wartime" scenarios. I revisited it recently wondering if I was just missing something back when I was younger, but nope. On the harder levels it asks you to sustain larger and larger populations with increasingly limited resources, and reaching the level of getting patrician housing (only achieved with sustained, stable access to literally every amenity) is extremely difficult but oh so satisfying. Every other city builder I've played, I barely have to think about every house becoming the top tier, but in Caesar 3 it's impressive if even a single block achieves it. It stands out even now after so many new entrants into the genre. Hell, it's still worth playing haha.

Out of the games I've played, OSU. I am pretty average at rhythm games where it's like Project Sekai or the Miku Diva style games where all you have to do it wait and click a button or tap somewhere specific at a fixed location on screen, but I absolutely suck at the whole move the mouse and click thing. Just as bad with mouse as when I tried with my beginners tablet.

Most other games I play anymore are games I know I'm at least decent at, so I don't have many games I'd consider the hardest or even to compare those too. Though, while writing this and thinking about it, I'd say I might compare OSU to Vib-Ribbon in general, default songs or not, and possibly even give it a close second for difficulty. And that's despite it being more of a wait and click type rhythm game in my eyes.

Old games were brutal.

Jet set willie comes to mind.

Battletoads

Army Moves on the ZX Spectrum. I tried that game on and off for years, and I think I beat the first level once.

The games you have to grind for 1000 hours just to have anything worthwhile. I got to be able to turn it on and go Brrap Brrap Pew Pew!

Nina Gaiden 2. Bayou Billy.

Freeways is a great game that makes me want to tear my hair out.

Resident evil revelations on inferno difficulty is just unfair.

Polybius I forget what I’m doing while playing.

A lot of games made in the 90’s were difficult. But that’s before entitlement struck the gaming community and the “I need to beat this game in a weekend” turds were dictating how games turned out.