(Stats): Lucario is faster, stronger, has more attack variety, is just as, if not more durable, and has far superior range.
(More in depth) While Cinder's fire attacks would be a problem, it's not a massive strain of intelligence to recognize your weaknesses.
Speaking of intelligance, while Lucario's isn't exactly measured, it's probably at least comparable to a human, considering its capacity for speech and planning. Cinder's flight is partially negated due to Lucario's ability to jump and fire projectiles (Aura Sphere will never miss, negating the best aspect of flight, dodging attacks in three dimensions of space freely, rather than two.) As Lucario is starting in Mega, I am assuming it is used to this form.
While Lucario's not leaving unscathed, it (gender not specified) will leave alive. Burned, yes. Injured? Of course. Victorious, yes.
Cinder's lava Dust and Fire Manipulation may prove troublesome for Lucario, but he has superior range, and the fact he has the movement speed advantage and Extreme Speed will keep it that way if he's smart enough to use it to his advantage. I'll hand it to Lucario more times than not.