Elwind in the right hands can be deadly. Sometimes when I try to edge-guard with it, it'll just bounce them up. However, occasionally it'll launch them sideways into the side of the stage and they'll fly down and get KO'd. Even less frequently, they'll fly with the Elwind and get dragged down. It's not reliable per se, but if you can use it safely without leaving Robin vulnerable, I say go for it. Worst case scenario, you still deal ~10% to them (or you save them, but in that case, you shouldn't use it at all). Also, the trick is to aim nearer to Robin's body with it. I find myself miscalculating all the time and accidentally floating too high up and missing them completely. (EDIT: I've been experimenting in training mode with it and it's hard to hit with, but it's much easier to do so on a stage with a box shape, like Gerudo Valley's Final Destination. This makes even the sideways hits much more deadly since they'll bounce off the stage's edge and fly downwards often)
However, I've meteor smashed/spiked (I'm not sure of the difference but the opponent went straight down) with Levin Sword Dair. Yeah, it can launch the enemy sideways (sometimes for a nice KO), but if you get the timing right, it can send them plummeting downwards. I almost prefer it to Elwind as an edge-guarding tool. I haven't seen this mentioned here...