Tough call since I finished some pretty tough games. Would be easier to tell wich game was the hardest to 100%.

I will say it was donald duck as cold shadow (AKA maui malard or something) on PC. keyboard controls made it particularly hard. Also, wonder boy 3 for master system.

Maybe it wasnt really the hardest game that i have played, but FF X was the most punishing game for me.I had to create strategies for a lot of bosses because they would simply pwn me otherwise.I still have nightmares with the final boss.

Pulstar

Hard to say... don't recall playing game overly hard but when I was little, I struggled to get past the first Goomba in the original Super Mario Bros

Atm, Ace Attorney is challenging because I always select the wrong answer :p

I beat all of the NES Castlevanias, Ninja Gaidens, and a few others that were super hard. At the time, that's what we did. These days, I suck so much.... Just thinking about replaying a game like TMNT stresses me out!

Ninja Giaden Black on the original Xbox. Also Dark Souls/Demon Souls.

I think it was COD 4 on Veteran difficulty. It was really really hard.

Bucky o hare on the nes, made me want to pull out my hair.

Oh yeah. Bayou Billy.  I got that came because it tried to do so much.  It had crazy variety but damn, it was hard. Especially the driving parts.  Would break my thumbs! I did beat it, though.  Probably the time in my life. Once, without the whip. That game. You die once and lose your powerups (whip, bullet proof vest, meat) and you're screwed.  It was either never die or die and start over.

I Wanna Be The Guy for me