Pokémon S17E31 - The Aura Storm!

Having found the Lucarionite in the cave, Korrina meets up with her grandfather, the Mega Evolution Guru Gurkinn. To test Lucario's new power as Mega Lucario, Korrina and Ash decide to battle. However, when Lucario's power is stronger than it can handle, it loses control of its Aura and starts getting more and more brutal. Korrina and Ash try to stop Lucario, but it keeps mercilessly beating Pikachu. Will they manage to control Mega Lucario?