I was a lucky kid growing up, while the other kids in my school played on their game boys (those really old ones without color) me and my older brother was playing on a commodore amiga 500. We had a ton of games for it and even thought none of us could read english back then we managed to trial and error our way to figuring out how to play and even beat some games, usually because they had built in cheats. They were not easy, let me tell ya. Some of them would even give arcade games a run for their money in sheer difficulty.
While I have forgotten most of them, there are three that stand out in my mind even to this day and that was because how different they were and of course: their bosses.
From left to right: The mage of bubble bobble resting on the 100th floor, only my brother and his best friend managed to get to and beat this guy and it took them years to accomplish this feat. I have seen them blow through the first thirty stages perfectly synchronized it was kind of amazing to watch and indicative of the sheer effort it takes to beat that game.
The minotaur of rodland (we mistakenly called it rodoland until we looked it up online) none of us has beaten him without the built in cheats. He is a monstrous four stage boss, getting increasingly larger and more dangerous with each progressing one, culminating in him becoming a titan, filling the entire vertical space and towering over you, many times your height.
And the Vizier of Arabian Nights. Only one of the three I managed to beat legitimately. Honestly after the harrowing adventure to get to him he is kind of a pushover if you got a decent amount of health left. He switches between air, earth, water and fire attributes. Each state has it's own tricks, but none of them are particularly dangerous if you don't mind tanking a few hits. Still I felt really good the first time I beat him, even if the journey up to him had been far harder an obstacle.