Another challenge in a game that took me years to defeat was the final boss of Dragon: The Bruce Lee Story.
While I usually defeat him nowadays, The Phantom was an absolute pain back then, with his giant scythe which he could hit you with at unfair distances. Not only that but it only took him about 6 hits to wipe out your health bar. Defeating The Phantom took alot of patience, and non stop movement, especially when he starts using one of the cheapest boss fight tricks and starts teleporting.
While the fight is tough enough, theres even more to it. I remember the first time I emptied his health bar... He kept fighting, and no matter how many times I hit him he wouldnt die. He would simply clutch his face for a moment everytime I hit him, but wouldnt die. For years I would keep fighting him, trying to find out if it was possible to beat him, and for a while I simply concluded he was unbeatable (I was not the only one).
Then it happened, I was fighting him, depleted his health and switched from normal fighting mode to nunchuck mode, I kept hitting him with the powerful nunchuck attack and then accidentally pressed a different button. There is a certain nunchuck attack that is very small, never hits any one and is seemingly useless, when I accidentally used it near The Phantom, Bruce jumped over him and strangled The Phantom with them. I have to praise the game for that, there is a walkthrough on gamefaqs that has concluded that The Phantom is unbeatable. But it is rather creative to have such a strange way to defeat him (though not strange at all, as it is exactly what happened in the movie).
I was so satisfied when I beat this guy, it was a very difficult moment.