Wii Fit Trainer (SSBU)/Forward aerial
Wii Fit Trainer performs a Single-Leg Extension, stretching an arm diagonally forward and upward as well as a leg diagonally backward and downward. This move, like many of Wii Fit Trainer's other attacks, has hitboxes both in front of and behind her simultaneously, with different effects on both side. The front-facing arm hit of the attack launches the opponent diagonally upward, while the back-facing foot hit has a weak meteor effect. The arm hit has low base knockback but high scaling knockback, making it both a good combo tool at low and mid percents and a good kill move at high percents, especially when used as an edgeguard tool. It also has a moderate disjoint, as the hitbox surrounding Wii Fit Trainer's outstretched hand is rather large. The foot hit has fairly low knockback and a small hitbox, but it somewhat makes up for these shortcomings with its speed, being one of the fastest spiking attacks in the game at frame 9.
Forward aerial's biggest strength is its great frame data, something that few of Wii Fit Trainer's attacks possess. Although the move's startup is fairly average, its ending lag, landing lag, and autocancel windows are all excellent, allowing the move to be used with very little commitment. This lack of lag was only further accentuated in Update 8.0.0, when both ending and landing lag were further reduced, consequently creating an even better autocancel window. All these strengths result in the move being as safe as -2 on shield (-1 when Deep Breathing is active), lagless enough to squeeze out a back aerial before landing from a short hop, and also a niche kill confirm setup.
Both the front and back hits of forward aerial can be used as a kill confirm setup if they connect as Wii Fit Trainer lands, but generally speaking the foot hit is more reliable. In particular, landing with foot forward aerial true combos into forward smash at a large percent range with zero opportunity for the opponent to escape, since the move's low knockback does not send them into tumble, resulting in easy kills at mid percents. At later percents when the foot hit does spike, landing with the move true combos into forward tilt, RAR back aerial, etc. When near the ledge, landing with the arm hit of forward aerial can also lead into a down aerial for especially early kills.
Forward aerial's one large weakness is its notable lack of any sort of coverage directly in front of Wii Fit Trainer, unlike virtually every other forward aerial in the game. This makes it slightly harder for Wii Fit Trainer to successfully challenge opponents in front of her at close range, as well as cover the ground in front of her as she lands. Although there are many followups for landing with the arm hit of fair, there are many characters and situations in which the attack simply will not connect. The small hitbox at Wii Fit Trainer's center helps remedy this blindspot issue slightly, but since it's only active for a single frame it is still often troublesome to hit opponents horizontally with forward aerial.