Vilness's Nessgeguard shows some really good options(The PKT2 ledge sweetspot is REALLY nice) Dtilt is always an option, though you have to be careful which character you use it against, as is tailwhipping though that requires a lot of skil. PK Flash is incredibly situational, as is the F-smash(which requires great spacing against a good opponent). I think going after the enemy with the f-air is probably the overall best bet in most situation, you just have to practice it enough so you can always get back to the edge. Ness requires a lot of practice, spacing, and knowledge in his edgeguarding. At least....as far as I've seen. I'm still not practiced enough in ANY of the techniques I just mentioned, I've only succeeded with the F-smash or dtilt edgeguards and even those I've only managed to pull off once or twice. I'm simply repeating what I've been told, what I've seen, and my own assumptions based on a higher level of skill.