The question of the most powerful sword in 'RWBY' is a fun rabbit hole to dive into! There are a few standout contenders, but I'd argue that Crocea Mors, Jaune Arc's family heirloom, has some serious hidden potential. It might not seem flashy compared to, say, Qrow's Harbinger or even Ruby's Crescent Rose, but its versatility is insane—it transforms between a sword and a shield, and Jaune's Semblance (Aura Amplification) could theoretically supercharge it beyond normal limits. Plus, the emotional weight behind it—being passed down through generations—adds a layer of 'narrative power' that often translates to literal power in storytelling.
Then there's Maria's Life and Death, a pair of blades that are basically the pinnacle of pre-Great War technology. They're fast, deadly, and integrated with her Semblance in a way most weapons aren't. But honestly? The 'most powerful' sword might not even be a traditional one—Adam Taurus' Moonslice, while technically a katana, is less about the blade itself and more about how his Semblance turns it into a literal energy cannon. It's terrifying in the right hands, especially during his fight at Beacon. Still, I keep circling back to Crocea Mors because of how it grows alongside Jaune—it feels like it's got untapped legend-tier potential waiting for the right moment.