This is an easy one for me. In Shinobi for the PS2, as you beat the game, different difficulties become available. It goes from Normal to Hard to Super. At first, I thought the final boss on Normal was hard. Then I got to Super. It took me roughly a year to a year and a half to finally beat the final boss on Super! Sometimes, I would die 30 times a day, 7 days a week. Finally, one sunny morning, I figure what the heck. I'll give it a another whirl. It was lookin' pretty much the same for the first 10 deaths. Then, suddenly, I realized I had depleted 90% of his energy. Then... 95. And then, the moment of truth... with one final shuriken to the bastard's neck, 100%. On that day, I felt better than I had for a really long time. He was truly the hardest boss ever.