It involves the Mii Swordfighter lifting his/her sword and unleashing many low-knockback crescents of random colors in a chosen direction. It is similar to Wii Fit, and bears a resemblance to the Sword Beam from The Legend of Zelda series. Compared to Wii Fit, Final Edge is much weaker, each slash dealing mediocre knockback, designed to overcome foes with its sheer number of slashes and drag them offstage for a KO.
This Final Smash behaves slightly differently between both versions of SSB4. Final Edge on the Wii U makes the crescents follow a wider path, giving it more vertical range and less accuracy than on the 3DS. In both versions, however, the Swordfighter can unleash a powerful blow from its sword to anyone very close to it as it initiates the attack. This hitbox can KO opponents at moderate damage percentages.
In Ultimate, the move was given an aesthetic change, which now involves the Swordfighter physically slashing their sword to release the crescents. The move now seems to be performed faster because of this. Unfortunately, the Final Smash has less range than it did before making it less consistent for KOs.