Lucario Bair is a reliable kill, if you can land it. It's like I said somewhere before: Lucairo's Bair takes so long to wind up and lasts for so few frames, that if it does land, either the opponent wasn't paying attention and deserves to be KOed, or the Lucario player got the mother of all reads and deserves to have that KO.
FP is also a reliable kill, if Lucario is in grabbing range.
It's kind of a common theme with Lucario, that all of his reliable kill options come with strings attached, and not just "he has to be at high % to kill" either. I personally have gotten, if not a majority, than a large plurality of my kills with Lucario by ASing my opponent when they're off-stage.
Then again, after all the practice I've put in, I've become a frighteningly deadly shot with Aura Sphere. Seriously though, I've pulled off shots that required either blind luck, or really good predictions/reading against the opponent.