Warning! Spoilers for One-Punch Man Chapter 143 ahead!
One-Punch Man is known for having an array of bizarre and sometimes problematic characters, but even among those, S-class's rank 11, Superalloy Blackluster, has stood out. While Blackluster (known in Japanese as "Darkshine") appears briefly in the anime adaptation, he has done little more than pose and show off his muscular body, and his run-in with the hero hunter Garou ends in disappointment. In Chapter 143 of the manga, however, Blackluster gets to show off just why he deserves his high ranking.
Although the heroes' battle against the Monster Association is finally starting to turn in their favor, it's still been an uphill battle. Some of the executive-level monsters are perfectly suited to fighting certain heroes, as Atomic Samurai has learned the hard way. His blade is rendered useless against the formless nature of Evil Natural Water, and it actually aids Black Sperm early on by causing it to multiply. Evil Natural Water's attacks have proven particularly difficult to handle, as it fires off jets of water that move so fast that characters who easily dodge bullets have trouble evading them. The monster is considered so dangerous that even the Monster Association has kept it locked up.
While Atomic Samurai and his follower Iaian struggle with Evil Natural Water, Blackluster enters the fray in dramatic fashion, tanking several of the water jets at once to protect Iaian and emerging unscathed. Blackluster's nearly impenetrable skin reacts to this as if it were little more than a pressure wash, sparkling even brighter. He then counters with an attack of his own, seemingly destroying the monster in a single hit.
Of course, Evil Natural Water isn't likely to be gone for good so easily, but given how it has been almost immune to physical attacks up to this point, Blackluster's ability to dissipate it into tiny drops of water makes for a seriously impressive feat. Evil Natural Water's jet attacks have also been shown punching holes in everything from armor to concrete walls, killing ordinary humans and causing immense damage to even the toughest opponents. Blackluster's strength and resilience here in this fight place him on a level that only Saitama (and presumably number one ranked hero, Blast) has exceeded thus far, showing that he truly deserves his spot high on the rankings. The chapter ends with Blackluster squaring off against Black Sperm, so it seems his moment in the spotlight isn't over quite yet.
As the heroes begin to mix up what monsters they've been facing, like Blackluster does in this chapter of One-Punch Man, it's become apparent that in much the same way that some monsters are perfectly matched against certain heroes, there are also other heroes out there who can effectively counter that same monster. This teamwork and cooperation has been key to the heroes' efforts to turn the tide, and even if Evil Natural Water should return once again, Blackluster's abilities have bought the heroes some much needed time to deal with the other executive monsters, like the newly powered-up Fuhrer Ugly.