While the title characters of Miraculous: The Tales of Ladybug & Cat Noir are off saving Paris with flashy transformations and super moves, it's easy to overlook the source of the powers that allow them to do it all. In fact, the beings that grant them such powers, Kwamis, are much more powerful than we give them credit for. Plagg, in particular, the Kwami of destruction, has devastating historical notoriety, maybe even qualifying as apocalyptic territory.
Plagg's Unlucky Powers Apparently Wiped Out the Dinosaurs - and More
Kwamis are ancient and immortal beings, referenced to have existed since the dawn of time. And although their existence is kept secret from the public, their presence can be found sprinkled across history. Aside from being incredibly adorable, they each embody a unique superpower that they can share with others through their respective Miraculous. They do this by transforming their Miraculous owner into an animal-themed being capable of wielding such magical prowess.
Plagg, unluckily, has powers that are potent enough to cause significant damage, even without meaning to. In Season 2, Episode 21, "Style Queen: Queen's Battle Part 1," it is mentioned that Plagg is solely responsible for the leaning of the Tower of Pisa, the sinking of Atlantis, and most shockingly, the extinction of the dinosaurs. With this reputation, Master Fu, the guardian of the Miraculous, deems that Plagg is too dangerous to use his powers without an owner.
While Kwamis aren't typically seen using their powers themselves, in the same episode, Plagg uses Cataclysm by himself to assist Ladybug in a dire situation. He uses his signature super move on the Eiffel Tower, causing the structure to crack severely and become unstable, toppling onto a nearby bridge and surrounding buildings (Ladybug fixed the damage in the end as usual). Based on this, as well as Plagg's backstory, this affirms that Plagg is one of the most capable, yet dangerous Kwamis in existence. He is the very embodiment of destruction.
Cat Noir Only Uses a Fraction of Plagg's True Power
When Cat Noir uses Cataclysm, however, the destruction he inflicts is on a much smaller scale, destroying objects, corroding parts of buildings and malfunctioning technological equipment. While it can still kill, and thus is still incredibly dangerous, the damage done is more controlled compared to Plagg, whose control is clearly limited.
That being said, Cat Noir can only exhibit only a fraction of what Plagg can, wielding the powers of the Cat Miraculous in a way that's restricted, which ultimately has a better chance of preventing calamity. This implies that every Kwami is much more powerful than their Miraculous owners. While it is unknown if other Kwamis need an owner to keep their powers under control like Plagg, the main reason for having human Miraculous owners seems to be to keep the existence of Kwamis a secret, using humans as their conduits instead.
Did Tikki Correct Plagg's Destructive Mistakes in the Past?
Relating to Plagg's powers having a great (negative) impact on human history, there is an interesting fan theory speculating that Tikki, the Kwami of Creation and Plagg's opposite, may have created humans to make up for Plagg's error following the extinction of dinosaurs. This theory was suggested by a Reddit user and actually holds a lot of weight. Since Tikki and Plagg are opposites, it is likely that the intensity of their abilities is equal. This is supported by the extent of Ladybug's powers, as she is able to fix any bit of damage caused by their fights against Hawk Moth no matter how substantial.
Looking at the immense possibilities of Plagg's powers, it's reassuring to know that the Cat Miraculous is entrusted to someone who uses it to be a hero, utilizing it with compassion and mercy. The show even has Cat Noir grapple with the consequences of what Cataclysm can do with a single misstep in Miraculous World: New York, United Heroez, solidifying the responsibility that comes with possessing any superpower -- especially one capable of total disaster. It's fascinating to see Cat Noir use these powers with a destructive history as a means for good now.