Critical Hit (必殺の一撃 Hissatsu no Ichigeki, Sure-Killing Blow) is Marth's Final Smash in Super Smash Bros. Brawl; it is by far the strongest Final Smash in Brawl, and its power and damage also make it one of the strongest attacks in all of the games. The animation is similar to that of Marth's critical hit animation from the first Fire Emblem game. It deals 62% damage, resulting in the knockback being enough to KO any character at 0% under most normal circumstances. The power of this move is countered somewhat by its larger time frame in which to perform a dodge (the time during which Marth raises his sword), though it is still relatively fast. The best time to hit an opponent is when they have just recovered and are falling. If it hits, an HP gauge from Fire Emblem is displayed alongside each hit character, which starts at full and quickly drops to zero.
Until the attack animation completely ends, the entire sword carries the move's hitbox, meaning that the attack can also hit anyone directly behind Marth when Marth swings his sword. Rolling around Marth is not recommended. On the ground, the attack will follow the platform's contours, and the move will end without Marth swinging if he reaches the edge. Missing with this attack on the ground on a walk-off stage, or in the air without any intervening terrain, usually results in a self-destruct, as the dash Marth performs during the move is approximately the same distance as the width of the largest area available in the Stage Builder. However, this can be avoided by pressing an attack button, which will stop the dash and trigger the strike immediately.
Since the move is nothing more than a single hit, launch resistance such as that gained from using Aether can be used to survive, providing good timing. Of course, this will not stop the target from taking the move's full damage. Characters can also dodge this attack by sidestepping or using an air dodge; Marth will try to attack the dodging character but will miss.
Despite is ridiculous power, Critical Hit has earned the reputation of being one of the most predictable and avoidable Final Smashes due to its slow startup time and introduction sequence, which gives all other players in range the chance to completely dodge the move.
This attack has such immense knockback that is possible to KO someone else by being knocked into them after being hit by the critical hit.
 Trophy Description
Marth's Final Smash. He thrusts his sword skyward, then rushes to meet his targeted enemy with furious speed. The blow he strikes is so powerful that his foe is instantly launched off the screen. As in Fire Emblem, a window appears that shows the character's hit points dropping rapidly to zero--but this is just for effect. Smash Bros. does not use a hit-point system.
The critical hit is a staple feature of the Fire Emblem game series, which inflicts three times the standard damage if performed, accompanied by a unique attack animation. The animation for this Final Smash was likely inspired by the critical hit animations of the various Lords in the series' past. The gauge that appears represents the Hit Point system used in the series, and it has a graphical style similar to those of Fire Emblem: Radiant Dawn.