malcolm is right on a lot of point but i think hes wrong in places too.
1. luc doesnt have THAT many killing options. I personally think its your fault if you die from his n air. both characters have to be at pretty high percents for back air, up air, or up tilt, depending on postioning on the stage. and good lucs, should rarely use up smash or down smash. luc has to see way way ahead of time to even hit with up smash. however i think if you pull too many spring down airs, or too many HAs, both of those are great oppurtunities for luc to upsmash sonic.
2. the down air, lucarios love and will use it at just about every opputunity, however sonic has to mobility necessary to bait a down air and hit lucario around it, and its a semi hard thing to learn that is invaluable for sonic in the match.
3. i dont see how having 1 chargeable projectile makes lucario a camping fortress, because it seems that that would make pit samus and falco matches unwinnable for sonic.
4. i think you just have to play patient, lucario isnt a laggy character, but sonic is a character that makes lucario way more punishable than he usually is, thats what makes sonic good.
5. learn to instant dash attack out of shield, if you are good at it, you can punish lucs f smash.
6. 55-45 in lucarios favor, they go back and forth and trade damage but the aura will many times let luc kill sonic before sonic kills luc. but when you kill luc first, it makes it harder for luc to kill sonic cause he will be weak from the damage reset