Template:Infobox Final Smash SSB4 Mega Lucario (メガルカリオ, Megarukario), known officially as Mega Evolution, is the Mega Evolution of Lucario in the Pokémon games. It appears in Super Smash Bros. 4 as Lucario's Final Smash, replacing Aura Storm. When Lucario activates its Final Smash, it will shout "Max Aura!", then it'll transform into Mega Lucario. Mega Lucario's aura attacks are always at maximum power, regardless of Lucario's current damage.
Description from the 3DS version's foldout
"Evolve into Mega Lucario. Aura power rises to max."
Origin
Mega Evolutions are a mechanic introduced in Pokémon X and Y. Only a small amount of fully evolved Pokémon including Lucario can Mega Evolve, as long as it holds a special Mega Stone unique to its species. For Lucario, its Mega Stone is called Lucarionite.
A notable instance where Lucario could Mega Evolve was during the final battle against Korrina, the third Gym Leader, who not only gave the player one of her Lucario, but also had them fight. Both Lucario could Mega Evolve during the battle, acting as the player's tutorial for how Mega Evolution worked. It has also been stated in the game that Lucario was the first Pokémon to be able to Mega Evolve.