Directional - These Final Smashes launch an attack in a single direction, which may or may not be controlled. This kind of Final Smash has a blind spot, usually behind the attacker, where targets can hide.
Final Form - These Final Smashes involve the character transforming, temporarily gaining a new, stronger moveset that can quickly KO opponents. The transformations usually buff up the character's existing moveset, but can sometimes give them different attacks.
Semi-Final Form - These Final Smashes involve a character transforming, but they cannot be controlled to the extent of a regular final form. Typically, they have a moveset consisting of 1-3 attacks.
Trapping - These Final Smashes attack a certain area, grab anyone inside said area (or just a single character), and lay down an inescapable beating. They generally have a small initial range, and will fail if there are no targets caught.