WARNING: The following article contains spoilers for One-Punch Man Season 2, Episode 12, "Cleaning Up the Disciple's Mess," available now on Hulu.
Humanity faced two separate new threats throughout One-Punch Man's second season. The hero hunter Garou stalked and defeated members of the Hero Association, and several monsters formed their own rival organization, the aptly named Monster Association, to bring about a prophesied apocalypse by targeting major human cities and overwhelming their defenders.
While the apocalypse may have been postponed for the foreseeable future, and Garou has been dealt his most crushing loss yet, the second season of the popular anime series ends on a bit of cliffhanger, with several major plot threads left unresolved.
Picking up from the previous episode, Garou -- the self-proclaimed human monster -- has finally been tracked down by the S-class hero Genos, Garou's former martial arts mentor Bang, and his older brother Bomb. The past several episodes have increasingly worn down the Season 2 antagonist, with him facing back-to-back defeats at the hands of Watchdog Man and Saitama. Exhausted and still recovering from the earlier battles, Garou has still proved formidable, taking out a group of A-class heroes that cornered him. However, Genos and Bang delivered a beatdown to the powerful martial artist.
Before Genos can deal the finishing blow, however, Garou receives timely aid from the Monster Association itself, led by Phoenix Man and Elder Centipede. The Monster Association had its eye on Garou for some time, due to his success in defeating several heroes over the course of the season; the group even offered him a chance to transform into an actual monster through the use of monster cells and join its ranks. In a surprise move, after idolizing and identifying with monsters his entire life, Garou actually rebuffed their initial offer, preferring to continue his hunt as a human.
With the Monster Association later coercing several martial artists to transform, Garou may no longer have a choice, as Phoenix Man flies away with the barely conscious hero hunter to the Monster Association's secret headquarters to meet with the organization's leader, Orochi. And if Garou is forced to consume monster cells to become a monster, he would receive a significant power upgrade, which could make him more than a match for Genos and Bang in an inevitable rematch.
Covering Phoenix Man and Garou's escape is Elder Centipede, the unstoppable monster that had defeated Metal Bat in an earlier rampage through a city. A looming behemoth with much of its flying body protected by a impenetrable carapace, the monster is completely unimpeded by Genos. The cybernetic hero's most powerful upgrades and weapons barely leave a dent, as Elder Centipede reveals the ability to instantly regenerate from attacks. As Genos, Bang and Bomb attempt to flee the scene with the unconscious A-class heroes, Elder Centipede sets his sights on a nearby city for his latest path of destruction.
Distracted by the top-ranked hero King, Centipede diverts his attack at the last moment, only to be defeated by a single, massive blow from Saitama, who once again lives up to the series' title and premise. In awe of his mentor's raw power, Genos asks Saitama if he can ever hope to approach his teacher's strength. Unfazed, Saitama replies simply to gain more power, which Genos happily accepts, to King's dismay.
With that, Season 2 of One-Punch Man comes to an abrupt end, teasing an alliance between Garou and the Monster Association while Genos continues on his quest to be worthy of Saitama's attention. In short, the sophomore season served largely as 12 episodes of set-up, with its powerful protagonist largely distracted as the new threats of Garou and the Monster Association arose. While Garou and the Monster Association will presumably join forces for a third season, it's not clear how that confrontation, and its prophesied apocalypse, will go, but the world's best hope probably lies in Saitama's usual immense punching strength.