Final Cutter is an ability of Kirby's that's found in the Kirby and Super Smash Bros. series. In the Kirby series, the protagonist would gain this ability if he inhaled a Sir Kibble, while in the Smash Bros. series he had it automatically.
When Kirby engulfs a Sir Kibble, he would gain this attack as a part of Cutter Kirby. He'd be able to thrust sharp blades at his opponents in any direction, though would lose the ability if attacked. The Final Cutter specifically is the finishing move to the Cutter melee combo. In later games (notably Kirby's Dream Land 3) he'd gain this ability when he sucked in a Kaper Bukiset or a Poppy Bros..
Super Smash Bros. series
In the Super Smash Bros. series, Kirby is capable of using a cutter, jumping high in the air and then pounding the ground with it, which will send a shockwave through the stage for a short distance as well. The sword hits best at startup and the end before the shockwave. The sword has a slight meteor smash effect if sweetspot on the way down as well.
In Super Smash Bros. for Nintendo 3DS and Wii U, with the introduction of Custom Moves, Kirby has 2 variations of Final Cutter.
- Wave Cutter - The blade deals no damage, but upon landing creates a rock wave with more power and range than the normal version
- Upper Cutter - Comes out faster and does more damage while traveling up, but leaves Kirby helpless on the way down