Final Smash Meter
Final Smash Meter is a feature in Super Smash Bros. Ultimate, available as a toggle in the Rules selection, which was revealed during the Smash Bros. Direct on August 8, 2018. It allows players to have a chargeable meter and unleash a weaker Final Smash when the meter is filled. It is similar to Super Meters from traditional fighting games.
When the Final Smash Meter is turned on, a colorful bar is present below each player's damage meter. The bar fills as a player gives and receives damage, similarly to Little Mac's Power Meter mechanic. Once a player fills their meter, they will enter Final Smash standby, and can unleash a less powerful version of their Final Smash compared to the regular version that is used with a Smash Ball.
This feature does not allow multiple players to use a Final Smash at once, even though multiple players can be in standby at the same time.