Jab 1
By itself, even with a Sakurai angle, this jab provides a decent neutral and can lead into other attacks, such as dash, s-tilt, d-tilt, f-smash, or grab. It can also be buffered to perform jab canceling. Still, it'd be nice if the Sakurai angle was non-existent, rather than waiting around 30% or higher to keep Samus safe. A jab should be able to connect from one to the next. It renders jab 2 meaningless, since the whole point of jab 2 is to knock the opponent away.
Dash
Dash attack is actually pretty good in Sm4sh and its FAF is lower. What would be a nice addition to this attack is some kind of shock wave so that this mimics Samus' speed booster as seen in Metroid: Other M. The model of the character is based after this game, so why not add that extra feature? It would allow Samus to do early dash attacks safely, since there would be a distance between her and her opponent. It could be compared to Ness' dash attack, where sparkly features are in front of him.
U-tilt
In SSBM, u-tilt had a FAF of 35 frames. In Sm4sh it has 40 frames. U-tilt needs to return to 35 frames. Ideally, I'd prefer 30 frames. Alternatively, u-tilt could be given a different design based on
Melee Counter. Instead of being active at frames 15-18, it could be active at frames 9-12.
S-tilt
In SSBM, s-tilt had a FAF of 30 frames. In Sm4sh it has 34 frames. S-tilt needs to return to 30 frames. This attack is already good because it keeps the opponent at a distance. The foot is a tipper, which kills at high percents.
D-tilt
In SSBB, d-tilt was able to kill. This was removed in Sm4sh. FAF is at frame 40, though in Melee it's at frame 39. It would be nice if this attack was reduced at least to 35 for FAF.
U-smash
The FAF for this attack is 57 frames, which isn't bad, considering SSBM had 59 frames total, but could be reduced to 58 frames. Still, this smash attack is only good against characters who are about Mario's height, but even against Mario, it doesn't have a guaranteed hit. The hitbox doesn't cover enough and characters overhead will hardly get hit.
The only two reasons why this attack connects is because it's either hitting a large character, or the attack isn't used often and surprises the opponent. Nevertheless, this attack doesn't have an auto-link angle. Samus needs to start low in the front and this attack should guarantee the consecutive hits using an auto-link angle. It's a kill move that doesn't get used often.
Since Metroid: Samus Returns was released, another option for u-smash could be
beam burst. I'm not going to say the beam should cover the distance it does in MSR, but it could at least be comparable to
Mii Gunner's u-air while Samus is grounded. This would allow Samus to also safely hit aerial opponents who have disjointed hitboxes, such as Link, Toon Link, or the FE characters in general.
S-smash
Arm cannons should be somewhat longer than the arm itself. In the Metroid Prime trilogy, it appears the arm cannon was at least somewhat longer than Samus arm. This
image is a good example. There are two problems with this smash attack in its current state. The first problem is that it still whiffs at times, especially against shorter characters. In SSBM, side smash had two blades come out. I don't think this is necessary.
What could happen instead is that as Samus thrusts her arm cannon forward, streams of flames from the muzzle surround the arm cannon like
this. The flames could expand a little more like
this, however. When side smash reaches its peak, the flames within the arm cannon could then expel like so in Sm4sh. This would give Samus' side smash a larger hitbox in both width and length.
D-smash
Did you know d-smash in SSBM could kill? I wonder why they took that away from Samus. Well, I think
Mii Gunner has a better d-smash. The problem with his/her d-smash is that it can whiff and it seems to be possible to avoid the final hit, even if the initial hit connects. If this attack could be given to Samus with the problems fixed, Samus would have her potential kill move again, and it would resemble her d-tilt more closely.
Screw attack
My biggest issue with this attack is that it doesn't always keep the opponent caught into the attack. Furthermore, when has Samus ever been left open after using her screw attack? If she's going to end up in a helpless animation, then I think she should do as my brother suggests (which is canonical) and have the screw attack continue to do its attack animation from start to finish. What I think could be cool is if Samus could use screw attack and go at any direction. In the battle against SA-X (a perfect copy of Samus), it's capable of
attacking like a circular saw.
Side special
Missiles and super missiles need to be reworked to behave more like an item, rather than a projectile. In other words, retain its projectile attributes, but make it like an item so that when it connects with something like Link's bombs, it doesn't blow up without blowing up Link's bombs. I'm tired of these specials being stopped with something like bombs or with something like a jab or some disjointed hitbox. Also, give Samus the ability to perform
short hop homing missile cancel (SHHMC), as well as fire
two super missiles (you can only fire one in Sm4sh). Also, make super missiles kill again like they did in SSBM.
Down special
All I want for this is Samus' bombs to detonate like a proximity bomb. It can retain its function as is, but make it so that anyone who touches it gets injured. Samus would be able to create a wall.
Grab
Grab needs to be faster. There's no reason Samus needs to swing her arm forward in order to use this. And why can't she just deactivate it after using it and missing? It should be as simple as turning off a flashlight.
Back throw
It seems like everyone, including characters who either lack physical strength, or never demonstrated superhuman strength, have a kill throw. Give Samus one kill throw at least, please. Back throw seems like it'd be a good one.