From the Super Mario Wiki
Ads keep the MarioWiki independent and free :)
Extreme Speed (written as ExtremeSpeed in Super Smash Bros. Brawl as it was in the Pokémon games at the time due to text limitations) is Lucario's up special move in the Super Smash Bros. series, starting in Super Smash Bros. Brawl, and is based on the Normal-type move in the Pokémon series. When used, Lucario launches high into the air. The move can be aimed while shooting up, making a sharp curve to the right or to the left. As he is capable of clinging to walls and jumping off of them, the move lets him easily jump to a wall. It also lets him easily grab ledges. However, Extreme Speed only damages opponents at its peak (not doing any damage in Super Smash Bros. Brawl) and lightly knocks them back. If this move ends in mid-air, Lucario will be put into a helpless state. In Super Smash Bros. for Nintendo 3DS / Wii U, this move is affected by Lucario's aura mechanic, increasing the distance Lucario travels the more damage he takes.
Super Smash Bros. for Nintendo 3DS / Wii U introduces two variants to Extreme Speed: Ride the Wind and Extreme Speed Attack. Ride the Wind allows Lucario to more easily control his direction as well as travel farther, but makes him move slower and deal no damage. Extreme Speed Attack removes the sweetspot and knockback, but makes the move an attack that consistently hits multiple times.