Warning: Contains spoilers for chapter #163 of One-Punch Man
The hit manga One-Punch Man finally revealed what could be the only weakness of its overpowered protagonist, Saitama. While possessing power, speed, and endurance above everyone and everything else that appeared in the series, Saitama lacks technique and proper combat training, which is being exploited by his most powerful opponent to date, the "Hero Hunter" Garou.
Fans of One-Punch Man know that this unique spin on the combat shonen genre is built around the premise that its protagonist is stronger than everyone else. Saitama's absurd power is often used in the series for comedic purposes, but it also pushed this successful manga by One and Yusuke Murata to develop its storytelling in unusual ways. The majority of the time, One-Punch Man is a superhero-themed shonen, portraying the battles of the professional heroes of the Hero Association against various monsters. The "regular" heroes have to struggle to beat their opponents, usually getting to the brink of defeat, until Saitama shows up and completely humiliates the villains. The series also put much effort into building up an antagonist Garou, a martial artist who, pushing his body beyond its physical limits time after time, gaining incredible power that makes him the most dangerous villain in the manga.
After a long buildup, the much-awaited fight between Saitama and Garou finally began. Like everyone else before him, Garou is shocked by Saitama's ridiculous strength, but he is quickly able to find out a way to deal with him. Chapter #163 shows that Garou's fighting style is actually throwing Saitama off his game, to the point that the bald hero has to admit that "the weird way" Garou moves is making him miss his punches. On his end, Garou recognizes Saitama's superior physical abilities, but he is still confident he can win because of his opponent's lack of technique. As a master martial artist, Garou can predict Saitama's movements and exploit his many openings.
Saitama, in fact, lacks any combat training. He relies on his monstrous physical abilities to win fights, and his so-called techniques are nothing more than regular punches or basic movements. Garou, on the other hand, developed his own unique fighting style, the Monster Calamity God Slayer Fist, the fusion of the many styles he has learned and absorbed during his battles. Garou's former master, the 3rd rank S-class hero Silver Fang, already showed how a supremely refined martial art can let a regular human defeat a monster with superior physical qualities. In this case, Garou also has a "monsterized" body - which keeps evolving the more the fight goes on - so he possesses the perfect combination of power and technique. Finally, he is aware that, no matter how tough Saitama is, his internal organs can still be damaged, and that's what he is aiming for.
However, despite Garou's best efforts, Saitama is still playing with him, holding back his power and pulling his punches, because he has already realized that Garou is not actually a monster. Saitama is not fighting to kill, like he does against regular monsters, but to make Garou realize his mistakes. In the original webcomic published by One, Garou was the only enemy who made Saitama get a little serious, but was still utterly defeated in the end. It will be interesting to see if the digital manga will follow the same story or, as it happened in the past, will take a different direction. Regardless of the outcome, Garou correctly identified that Saitama's only weakness (besides being terrible at video games) is his lack of technique and training in martial arts. Perhaps a future opponent, one even stronger than Garou, will be able to exploit Saitama's weak spot effectively, and finally give the bald protagonist of One-Punch Man the challenge he has been craving for so long.