Hardest game you have played?

Rogue/ Angaband/ Nethack/TOME(V2)/Other Rogue Likes (Does not include things like FTL which are not Roguelike IMO)

VVVVVV and Killing Floor Solo mode Hell on Earth difficulty

dr daisy pet vet

Danmaku death (it's a shooter that's incredibly hard and rage inducing) (similar to touhou)

Spacechem was so hard I quit on the 2nd level

Super Meat Boy and completing LEGO games in 100% D:

TMNT on nes, and for the series I would say, ninja gaiden, megaman, metal slug, contra, ghost and goblins, Touhou

Mine Sweeper on hardest difficulty...it always comes the point where you have to guess -.-

Ninja Gaiden II

The Unfair Platformer.

Phantasy Star - Master System

Myst V.

IWBTG! also known as "I wanna be the guy"

There are many hard games I've played, but from the top of my head I would say..
Battletoads in coop for NES.

touhou embodiment of scarlet devil on lunatic mode the bosses make people rage like hell

Toki : Going Apespit.
Though that was likely due to bad design.

I also remember Plok getting pretty difficult pretty quickly, especially once the path started to branch.

Minesweeper

From the games I remember Crash Bandicoot 1.

Evil Twin - charming story vs. shittiest controls ever!

Fallout new vegas hardmode, meeting deathclaws... Not funny

fortix..

Meaty Super Boy and Souls that are Dark

Super Meat Boy :D

Bloody Trapland for sure....

The original Rayman game.

Spectraball