Editing Power Meter

Once the bar is full, a loud bell sound reminiscent of those in a boxing ring plays, and the bar becomes a flashing "KO" sign, causing his [[neutral special move]], the [[Straight Lunge]], to be replaced with a powerful move named the '''[[Straight Lunge#KO Uppercut|KO Uppercut]]'''. While arguably intended to be a [[one-hit KO]] per its name, its base [[knockback]] is not quite high enough to OHKO at 0%, and reaches [[KO]] potential at about 30% when performed on the ground, although this is dependent on the [[weight]] of the character; the lightest character in ''Ultimate'', {{SSBU|Pichu}}, can get KO'd at 10%, whereas heavyweights like {{SSBU|Bowser}} or {{SSBU|King K. Rool}} do so at about 40%.

If Kirby inhales Little Mac, he copies Straight Lunge, but does not gain a Power Meter and therefore does not get the KO Uppercut move.

==Overview==

The Power Meter fills when it reaches 100 units. To visualize this, the meter is separated by ten arrows that represent ten units each. When receiving damage, the Power Meter is filled by units equivalent to how much damage the attack deals. For example, taking 10% will fill one arrow. However, when Little Mac deals damage, the power meter fills with units equivalent to the damage he deals with a ×0.3 multiplier. So if Little Mac deals 10%, he will only fill the Power Meter by three units. As a result, Little Mac will get KO Uppercut much more slowly should he be at an advantage, while he will get it quicker if he is losing, and both methods can stack. Overall, Little Mac is guaranteed to get KO Uppercut if he either deals 333.33...% or takes 100%. In the context of a regular game, Mac will usually get KO Uppercut from around 65%.  

Once full, the Power Meter immediately empties once the player presses the special button to perform a neutral special attack, whether KO Uppercut is used successfully or not. This means it can be depleted if the player spams the special button during [[hitstun]] or other inactionable states. It can also be lost when entering a door in [[Smash Run]]. Outside of these scenarios, the Power Meter will be emptied if Little Mac is [[KO]]'d, or — after four seconds of maintaining a filled Power Meter — sent [[tumbling]]. This means that maintaining the KO Uppercut often necessitates defensive, bait-and-punish gameplay. This is because in the context in which it's obtained, even weak aerial attacks can send Little Mac into tumble, in which he will lose what is likely his only opportunity to use it for that stock.

The Power Meter appears in the arcade and Super Nintendo installments of the ''Punch-Out!!'' series, where successfully landing punches to The Challenger/Little Mac's opponents fills the meter up, while getting hit decreases the meter. Once the meter was full, The Challenger/Little Mac can perform a powerful knockout blow to his opponent. In ''Mike Tyson's Punch-Out!!''/''Punch-Out! featuring Mr. Dream'' and ''Punch-Out!!'' for the Wii, the meter was replaced with the Star Punch System. In this release, getting hit causes Little Mac to lose all of the stars he has accumulated, which ''Smash'' directly references.

*There is an [https://youtu.be/K3JdCPrUhhg?t=211 unused KO Uppercut animation] for Giga Mac. A GIF of it can be [https://tcrf.net/Super_Smash_Bros._for_Wii_U/Unused_Animations#Giga_Mac seen here].