Gen 9 National Dex
Lucario @ Lucarionite / Life Orb
Ability: Steadfast
Tera Type: If @ Lucarionite: N/A - If @ Life Orb: Dragon / Flying
EVs: 4 HP / 252 Sp. Atk. / 252 Speed
Nature: Timid
Moves:
- Aura Sphere
- Dragon Pulse / Flash Cannon
- Vacuum Wave
- Dark Pulse / Flash Cannon / Shadow Ball
Explanation:
A Life Orb would be my other go-to option for an item if you already have another mega evolving Pokémon on your team - the Life Orb is supposed to make up for the lack of Mega Lucario's ability (Adaptability). The Steadfast ability is useful for switching into Fake Out users like Ambipom and Sneasler (Steadfast raises Speed when flinched). The EVs and Nature are to make Lucario as fast as possible, because the Life Orb or Adaptability would already cover SpA.
- Aura Sphere is a no-brainer - it's a powerful STAB move that's unable to miss.
- Dragon Pulse is powerful coverage, and Terastallizing Lucario into Dragon would not only give STAB to this move, but it would also make Lucario resist any incoming Fire-type attacks. Flash Cannon may be an objectively better choice for this slot though, due to the fact it's a STAB move that Lucario could still use after mega evolving.
- Vacuum Wave is a must-have - it's Lucario's only priority special move, and it has STAB.
- Dark Pulse / Flash Cannon / Shadow Ball are all just coverage, but Shadow Ball has proven the most useful to me, able to take down Pokémon like Annihilape and Flutter Mane.
NOTE: I'm not that competitive of a Pokémon player