A big fixture of the original Dragon Ball was the World Martial Arts Tournament, a contest that Goku participated in thrice before eventually winning prior to Dragon Ball Z. It took a back seat for much of the latter series while the grown-up Goku's attention turned to space, the afterlife, and (to a lesser extent) fatherhood. Eventually, Goku and most of his peers would exceed the average power of a World Tournament Finalist (themselves at the time included) astronomically, to the point that what were once some of the strongest fighters on Earth are treated as a joke by the series.
Enter Mr. Satan, also known as Hercule in English translations, though his real name is Mark. Mr. Satan is first introduced as a contender in the Cell Games, cheered on by the world as the winner of the most recent World Tournament, which Goku and his friends skipped. Extremely arrogant and initially unable to comprehend the Z Fighters' cosmic strength, he quickly becomes a comic relief character, meant to be a pastiche of how a real martial artist would feel inserted in the wacky world of Dragon Ball Z.
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Later on, Mr. Satan becomes an important supporting character. His daughter Videl marries Gohan, and he manages to befriend the unpredictable and ridiculously powerful Majin Buu. The Buu Saga sees him transform from a hilarious egomaniac into one of the series' best characters, his lack of power compensated by his remarkable ability to befriend those he meets. He still maintains his arrogance on the surface throughout the rest of the series and Dragon Ball Super and GT, but overall becomes much more well-rounded.
By all accounts, Mr. Satan looks incredibly weak, but this is mostly because of the insane
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