Samus's Fsmash is a very interesting move that can be used for a VARIETY of things, ranging from killing, to setting up gimps. Her fsmash can be tilted either down or up, or left as it as. Tilting the fsmash upwards gives it 1% more damage (14%), and more knockback, making it one of her best kill moves, HOWEVER, this also limits your options against small characters, since it can oftenly miss them, it's better for tall characters. Normal fsmash is a great kill move for smalls, it will ALWAYS hit them, and is a great damage racker on heavies. Tilted down fsmash is the weakest of the three types, however, it is BY FAR the most useful for gimps. It can knock opponents into a position where you can missle/zair gimp pretty easily without any major risk.
My major concern with this move however, is the ending lag. Now granted, for a smash, it comes out quite quickly, but the ending lag on it is pretty bad, and if the move is not spaced correctly, can be punished SEVERLY. I tend to use fsmash when im SURE it will land, or I won't be punished. The move has nice range, but nothing over the top, there is no disjoint on this move.
My BIGGEST concern, and this is major, is the fact that the move will MISS some characters when they are behind the cannon of your gun, I don't know why this happens, but it will occasionally miss, so I honestly prefer down tilt over it.
With all that said, its a multipurpose killer for Samus, with some a few flaws. Bottom of B imo.