Falco's laser? Snake's Utilt? WARIO'S WAFT!?
No, the move is Samus's zair.
First off, this move has excellent priority on it. You're not gonna beat it, ever. You may get a trade somewhere, but there's nothing you can do to it because it's super disjointed. Second, it is incredibly long-ranged. That thing has such excellent range on it, and I don't think anyone with a third of a half of their brain would disagree. Third, it auto-cancels, so you can use it at any range and get good results with it. Already you can see that this is an excellent move. It doesn't stop there.
This move can be used to recover. It doesn't put you into freefall, either. It can be used as a tool to help Samus defend against edgeguarders. Only good things in this area. It can KO and it does decent damage. Yes, 4% on a move like this is still decent, and it can even go to 7% with a sweetspot. Speaking of sweetspotting, this move can kill, so nobody can complain about that.
It refreshes the rest of Samus's moveset, which is much appreciated when it comes to someone like her. This move doesn't go stale, either. Again, that's a really nice thing to have on such a great move because it tells you to use it as often as possible, something that the developers of this game are against, apparently. It can take on things that most other moves either lose to or can be swatted out. Falco's lasers can be absorbed and reflected, and they also don't beat Samus out in anything but how hard they can be spammed and the range, and even then range is the only one that move has going for it over Samus's zair.
I don't need to go on. The rest of the moves in the game don't even compare to this.