Roger felt the power of the Cursed Sword during the battle with Bedivere.
The acquisition of this weapon was entirely accidental; in legend, it belonged to the Headless Knight. But in reality, the Headless Knight was nothing but a puppet under the control of the weapon.
As for the limits of this weapon, Roger did not know, but the several innate abilities of the weapon were all incredibly powerful and practical.
However, the Dark Energy within it was not something an ordinary person could withstand. Even Roger had only managed to wield the weapon by employing some clever tricks, and he was always careful of the corruption from the Dark Energy.
The more powerful, the more addictive.
It was a double-edged sword. In the battle with Bedivere, if it weren't for Goway's critical outburst of spirit at the crucial moment, sacrificing herself to awaken a moment of clarity in Roger,
the final outcome of the battle would have been uncertain.