Early chapters of Dragon Ball saw Goku lose to Master Roshi in a fight, and created a monster straight out of a horror movie.
While Master Roshi doesn’t stand a chance against Goku as it currently stands in the Dragon Ball universe (and actually hasn’t for quite some time), Roshi did defeat Goku during the Saiyan’s first ever martial arts tournament as a way to inspire the young fighter to keep training and keep getting stronger. In the end, Master Roshi was successful in his elaborate lesson, but the price was the creation of a terrifying new enemy who was seemingly ripped straight from the reel of a horror movie classic.
Goku first started his training with Master Roshi in the early pages of the Dragon Ball manga after he witnessed first hand the awesome power of Roshi’s patented Kamehameha technique and realized Roshi was someone who could help him achieve new levels of power. After a few short months of training, Goku grew in strength exponentially and even became powerful enough to challenge Roshi himself as being one of the strongest fighters on Earth. In an effort to curb Goku’s ego from growing too big–as he feared his hubris might hold him back from his true potential–Roshi secretly entered into a tournament that Goku had signed up for and defeated Goku, all to teach Goku that there will always be someone out there stronger than him no matter how powerful he gets.
In Dragon Ball chapter 119 by Akira Toriyama, three years have passed since the world martial arts tournament where Roshi beat Goku, and it was time again for another tournament to see if Roshi is still the strongest in the world or if another fighter is even more skilled. In one of the earlier matches, Roshi–who secretly signed up again for the same reasons he did the last time–is battling a literal horror movie monster brought to Dragon Ball: the Wolf Man–but with a twist. This character isn’t a human who changes into a werewolf under the light of a full moon, but a Man Wolf who changes into a full human under the light of a full moon–and for that reason, he hates Roshi enough to want to kill him despite the rules of the tournament strictly forbidding such action against fellow contestants.
In the first tournament, Goku transformed into a Great Ape under the light of the full moon, and to defeat Goku, Roshi blew up the moon using his Kamehameha technique which neutralized Goku’s Great Ape form forever. Unfortunately, he also deprived the Man Wolf the chance to ever turn into a human again as he could only do so during a full moon. In destroying one of the greatest threats to the planet–as Saiyan Great Apes can decimate entire worlds in a matter of hours–Roshi created a truly terrifying villain who wanted nothing more than to see Roshi dead.
While the Man Wolf proved to not be much of a fighter, the fact that he is literally a horror movie monster makes him initially scary and his violent blood lust towards Master Roshi makes him dangerous. By the end of their fight, however, Master Roshi was able to cure Man Wolf of his lycanthropic curse, but that was only after he created the terrifying Dragon Ball villain in the first place–a chain of events that all stemmed from the martial artist’s epic victory over Goku.