Ninja Gaiden 1&2 (NES)
Vagrant Story (PS1)

There's been a fair few. The hardest that comes to my, I suppose, is Super Ghouls n Ghosts. I don't know how I managed to gut through that as a teen, but it happened.

I like a good challenge, but I also don't love games that are unreasonably hard or cheap. I'm typically not one of those gamers that equates hard with good. I'd rather enjoy a game, that be yelling at it, lol.

I would have to say BattleToads on NES (not the Rare's Replay version)
That game.... so many deaths.

Teenage Mutant Ninja Turtles 1 on NES back in the days.

Probably Zelda II, that game was a test of sanity.

You're not missing out on much to be honest, I didn't really enjoy it a whole lot.

Probably bloodborne. The evil within was pretty tough too.

Also beat FFX and getting all summons and tidus's and yuna's ultimate weapons. That damn chocobo race is borderline insanity!!

The game looks pretty interesting to me, but I haven't been able to find a copy of it. I'd probably ragequit before beating it, though!

Bloodborne. That game was really tough.

Yeks, some of the ones you guys mentioned are really hard. METRO drives me insane.
When I finish a game I assume it is because it is a easy game. To me the hard games are the ones I never finish.