From reading Pikachu's match-up thread, I was able to pull out some helpful tidbits:
Pikachu has to do lots of damage before he can kill at all. Our aura boost abuses this immensely.
To avoid our AS, Pikachus will Pshield, if we throw another one, they jump. We could abuse this by throwing an AS ABOVE him, then punish him if he is smart enough to stay under it.
Keep Pikachu in the air whenever possible, our air game>his. We beat Pikachu in everything but our Uair, which he will punish us with Fair or Dair.
Pikachu’s ground game>our’s. They WILL use their Tjolt, so be prepared. DO NOT ROLL BEHIND PIKACHU, his Dsmash will rip you apart. Both of these will be used to attemt to aggravate you, which is not good for Lucarios as we cannot lose our cool for even a second.
To kill us, Pikachus will use either thunder or nair in the air, fsmash is added to this list when on the ground.
When using your fair, there are two different scenarios. On the ground and in the air. Now lucario beat pika in the air. So, fighting in the air is going to take some conditioning and some mind games. In the air, shieldpoke with the fair. Now, this is where the conditioning comes in. Start out with doing a FJ fair. Do not use your second jump until you have conditioned your opponent into thinking that you always use your first jump to shield poke at him. Then, when you are absolutely sure that you have conditioned your opponent, FH at them then DI away and use your double jump>fair after your opponent has either used an attack or landed.
^This is a common strategy taken from Pikachu’s match-up thread.