@BlackRainFire
I can see how he deserves a weakness. His options are insane, and he's got a great air and ground game. However his range is barely better than Mario's, and he barely has enough of a defense game to handle opposing pressure. Small shield, short dodges, and not that many options to punish OoS. A combo character that can't approach, or even have a good defense game to handle pressure while trying to approach, is going to be neutered by characters who can easily outrange them.
This is Lucario's main issue. He's hard pressed to approach characters with solid keep away games, good OoS options, or those with range that exceeds his. The other issue is too much emphasis on aura. I like the PMBR for how they handle many things about character balance, but just throwing an aura charge on him to approach and hopefully not whiff it at the beginning of each stock is questionable.
Other combo centered characters have significantly better options to force approaches or approach with. Falco can completely shut down the stage with SH lasers, ZSS has an unclankable paralyzer she can move with, and so forth. Lucario has a slow blue bubble with horrible end lag that's powershielded easily. This just completely baffles me how other characters have solid approach options that are capable of being used at any time, yet Lucario is stuck with the poor range on his attacks and a bad defense game.