What's the hardest game you ever played?

Black Ops 2, I don't think I have ever had another game that was so hard to get through... Not difficult, just a "WTF is this?" kind of thing...

Pacman

Volgarr the Viking. Too few savepoints. It could only be saved if you would finish a level. The checkpoints were also scarce and the game wouldn't get saved by reaching them (if you would exit the game, you would start again from the beginning of the level). The game was extremely hard and I couldn't even finish the first level. I may suck a bit, but it was extremely hard.

Unreal Tournament 99. I'm pretty sure Xan aimbotted/wallhacked regardless of difficulty.

There's also Eternal Daughter, but i've never actually finished it.

Overture

I'm so ashamed...I fail at dark souls first boss..yes I know, I suck..
One day I'll probably give it a new try because I really enjoy all the part before..

Definitely King's Field IV (PS2).

Wizardry IV.
It's by far the hardest RPG game ever created.

It's an old-school (or just plain old) tile-based dungeon crawler RPG. You start with no items in a 2X2 room with no door. Most people never make it out of that room. If you do make it out, there's a ghost wandering around that,if he ever touches you, is insta-perma-death. The vast majority of guardians are stronger than you, and merely saving the game causes them to respawn.
There are puzzles that cannot be solved unless you're very familiar with the earlier games.

Despite playing the earlier (and later) games quite a lot, it took me way too much time and effort to make it past the first level - and I never got any further than that

http://crpgaddict.blogspot.com/2010/10/wizardry-iv-paroled.html
http://lparchive.org/Wizardry-IV/
http://8bitwizard.blogspot.com/2013/02/retro-review-wizardry-iv-return-of.html

Hardest game that's actually fun would be Ghosts & Goblins

Call of Cthulhu®: Dark Corners of the Earth
http://store.steampowered.com/app/22340/

the impossible game

This question is more complicated than it appears, at least to me. There's lot's of different types of hard, from the challenging, but basically fair and ultimately doable full-game experiences like Dark Souls (or so I'm told... by everybody) to the unreasonably touchy and punishing little indie turds attempting to capitalize on the "hardcore" craze started by IWBTG (the bad example) and Meat Boy (the better example).
As such, I'm not sure if I can name a single "hardest" game I've played, but one that comes to mind is Fenix Rage. Clearly inspired by Meat Boy, it began as challenging but doable, and had some clear production value, which is more than I can say for many indie titles that market themselves as "hardcore". Unfortunately, it chased the ideal too far and soon became ludicrously and unfairly difficult, requiring practically pixel-perfect timing and dozens of super-accurate dashes and jumps in a row without dying. All this was compounded by the bizarre choice to not make the moving parts of a level reset when you die, requiring the player to judge their timing anew every life. This might not sound like a big issue, but to "get gud" at a level-based platformer like this one means constantly redoing the level, getting a better feel for it and how it flows each time, until you can finally beat it. This requires everything to be in the SAME PLACE EVERY TIME YOU RESTART, but the devs of Fenix rage elected not to do that because "it made for some interesting speedruns". This is a major pain and a big complaint of mine. A lot of the platforming required later on was so unreasonable that I probably still wouldn't have been able to beat the game if the respawn had been designed properly, but it certainly would have gone a ways toward salvaging my overall opinion of the game itself.

Major Havoc (1983 Atari)
https://www.youtube.com/watch?v=9n6I1KPxOfE

"Runnn", a game I'm making in RPGMaker. Fuck this, why is my own game punishing me so hard. ;_;

The original NES Ninja Gaiden. Birds man, birds.

First thing that comes to mind is VVVVV... I'm sure there are other harder games that I'm forgetting right now...

Life, it sucks.

Tetris. Never finished it. T_T

Game Over on Amstrad CPC 464. When you were killed, you started the level again but without the power ups you had collected in that run. I played it countless times just to reach the end of level 1, and then a boss big as half the screen stomped me to death in 2 seconds. I never played it again.

Faster Than Light is so often so annyoing and frustrating - cant describe how often I`d like to throw my keyboard into my monitor...

super meat boy - I got so frustrated with that game that I got it removed it from my library. not the best game for someone used to play TBS, RPG and grand strategy

for me it would be the Dark Souls series (i own 1 and 2), really cant be arsed (which is a shame coz i like the idea) with a game that requires so much time these days if im being honest. i have a job and a grandaughter, the latter taking up more of my (quality) time and rightly so, so when it comes to gaming it has to be short and sweet and that series doesnt really deliver on that front tbh.

real life russian roulette ;)

View attached image.