Ultimate Muscle had an odd ending. The show itself was based around professional wrestling, and the final battle, which was rewritten strictly to end the surprisingly popular dub run of the series. The ending in question was an epic, knock-out, drag-out brawl between the protagonist Kid Muscle, and his greatest rival and the show's primary anti-hero, Kevin Mask. It also was easily the most violent fight in the show's run (ironic, being that 4Kids was quite keen on censoring violence).
And while the ending was good, it was still a bit of a disappointment. You see, the manga went on with the story by having Kid Muscle lose the match, and have Kevin Mask become the reigning champion, with Kid Muscle going on a campaign of great matches and re-matches in order to earn another shot at the title. In the anime, Kid Muscle won by using a move that he invented on the spot (inventing brand new moves on the fly is something he has done at least three times in the show's run, and it's a trick that actually worked rather well in this series as opposed to seeming like an author's cop-out as it has in others).
It should be kept in mind that this is also the series where one of the most popular characters in the final season was Monsieur Cheeks, whose face was a backside and who made numerous butt-pun in a french accent. And again, amazingly, it worked. That's pretty much the theme of the show from top to bottom. Awful things that shouldn't be funny, shouldn't be entertaining, but somehow still are.