Against Snake, if you can get him on the edge you're gold. His options are amazingly bad there, which is why almost all Snake's recover High and on to the stage, but against a character such as Lucario who isn't known for killing via a gimp, you can at least set up a damage rack up scenario
-If he jumps from the edge, you can fair/nair him back to reset the situation, or to force a cypher.
-If he rolls, you can fair, nair, dair, f-smash, or really anything. Just make sure to send him back off the stage quickly.
-If he attacks, you power shield and knock him off again. Notice a pattern? =p
-If he does nothing, you wait. [Maybe a B reversal short charge of your Aura sphere to bait a movement.]
Your best chance of gimping Snake is early in a match when he's at a low percent. You need to be able to juggle him to where you can bait him into a jump. From there, don't let him touch the ground. [Fair seems to be great at this.] You'll have to use your bair/nair/dair off stage to knock him out of the cypher, but eventually he's going to continue to keep recovering lower, and lower. Allow him to think the edge is safe, and then start the damage cycle noted above, if you are unable to cypher gimp him.
If for whatever reason he has been forced to C4 recovery, you have the following options:
-Jump on him if you predict it and take the C4 away.
-Aura Sphere him if you have one charged.
-Jump off the stage towards the edge, and footstool his attempt to tech the stage.
You will most likely NOT kill a Snake, but you will be able to create a great damage mounting situation which can completely change the ebb and flow of the match. This is all going from matches against Lee Martin.