WARNING: The following contains spoilers for One-Punch Man Chapter 156, "2Bad," by One, Yusuke Murata, John Werry and James Gaubatz, available in English at Viz Media and Manga Plus.
S-Class heroes are the strongest fighters the Hero Association in One-Punch Man can dispatch, yet their battle strength greatly varies. Blast, the No. 1 hero, proves strong enough to deal with a being suspected to be God, and Terrible Tornado, the hero ranked directly below him, can literally twist a tower-sized clump of soil. However, the other S-Class heroes are having a hard time holding their ground against Monster Association executives, especially their fully transformed versions.
Metal Bat is arguably one of the weakest S-Class heroes, given the fact that he and Tank-top Master were the first ones Garo defeated prior to his monsterization and slew of power-ups. While Tank-top Master joined the other heroes soon enough to save a couple others, Metal Bat only returned to the frontlines after most of the battle was finished. However, the might he has shown during their bout against Centisennin in Chapter 156 proves he isn't just an S-Class hero by name.
One-Punch Man's surprising team-up of Metal Bat and his arch-nemesis Garo continued to fight against Centisennin, another iteration of a giant centipede monster, in the quest to save a helicopter filled with humans. The pair showered the giant beast with a rain of attacks, but the centipede's regenerative abilities prove to be a real drag. Their only chance at killing the monster was to crush it from head to tail at once, but such a feat is easier said than done.
One Shotter and Gearsper's combined attack provided the hero-half-monster duo a window to save the chopper, with Garo throwing it into a giant net. Sending the humans to safety enabled the pair to unleash their full power, and Centisennin beating up Metal Bat fueled the hero's strength. The pair continued their barrage, but their techniques resonated with each other this time around, amplifying both of their attacks' destructive abilities. Although Metal Bat ultimately collapsed, Garo was able to snag Centisennin's regeneration core and use it as bait to take the fight midair.
Metal Bat being able to keep up with Garo and providing a substantial amount of support and damage is proof of his strength. Given that the resonance between their attacks heightened their destructive ability, he still managed to damage Centisennin after receiving an ample amount of damage. However, his efforts don't necessarily imply that the hero is at par with the Hero Hunter. Garo did most of the damage to Centisennin while Metal Bat primarily served as support. Metal Bat also collapsed near the end, while Garo still had enough strength to, predictably, finish the giant centipede monster.
Although it can be argued that Metal Bat was literally just lying down in the hospital, it is also true that Garo just came out of a series of high-level fights. However, Metal Bat's efforts and contributions are not to be undermined. He may not be a match against Garo, but he definitely can hold a candle to the other S-Class heroes of One-Punch Man.
