I've played a great many games vs. my roommate/good friend/eternal smash rival, and have some observations I'd like to bring forward.
I've found two matchups that are particularly dangerous for Lucario:
1: Cpt. Falcon
In my experience so far, this has been an absolutely nerve-wracking matchup for me to go against with Lucario. Cpt. Falcon has excellent mobility and maneuverability, allowing him to rush-down, pressure, bait-and-switch punish. The mobility allows him to easily circumvent Lucario's zoning game, he also has more than enough speed and reach in his kit to easily punish Lucario's missed reads. On top of that, Cpt. Falcon has more than enough raw power in his KOing moves to knock Lucario out before ludicrous-aura starts to kick in. The slight heavyweight class for Falcon doesn't help Lucario's case much either.
I've done my best to play a very conservative reactionary game against my roommate's Falcon; anticipating his running grabs by catching him in reverse-ASC, getting the reads. It's still a very, very dangerous game of cat/mouse, and Lucario is the poor hapless mouse.
2: Link
I've only fought against a few good Links, but those few matches have been enough to convince me this will be a very tough nut for Lucario to crack. The main feature here is Link's multi-layered zoning: not only is there bombs bows and boomerangs galore, there's also a very hefty, long-reaching, quick-swinging Master Sword in the way, and the clawshot that can potentially punish shields during the close-in, plus the Hylian Shield can make Aura Sphere/Force Palm zoning practically moot. A prominent (if not primary) drawback vs. Lucario in this matchup is Lucario's pretty poor kit for closing distance vs. zoners like link, Lucario really doesn't have the inherent mobility to wedge himself inside all of Link's tools like many faster characters can. And to top it all off, Link comes stocked with a plethora of very powerful, very long-reaching KO moves that will easily knock Lucario out before ludicrous-aura kicks in.
so vs marth and Lucina what are you thoughts so far?
i think out ftilt is very good iun this mu
Played several matches against my roommate's excellent Marth. Marth, in good hands, can be quite dangerous for Lucario. The tippers give Marth startlingly potent kill power on some very quick F-smashes, and there's plenty of pressuring options Marth can bring to bear against an unwary Lucario.
My personal strategy has been twofold: 1) Zoning with AS (both weak and strong AS) and FP, when higher % aura allows FP to outrange much of Marth's swordplay 2) up-close boxing/grabs.
Lucario vs. Marth is a dangerous mu if you're not prepared for a very high-precision Marth player, but definitely not insurmountable. For one, Marth doesn't really have the kit to take advantage of Lucario's disadvantages as well as other chars can, particularly Lucario's less-than-stellar ability to work under a high-speed pressure game, since Marth is far better suited for precision punishing, and his spacing game is manageable with Lucario's tools. As an added bonus for Lucario, I've found AS to be an excellent way to harass Marth trying to return to stage after a ledgegrab; not as a single shot, but several carefully timed partial-charges, especially if there's a little aura built up.