Wii Fit Trainer (SSBU)/Neutral aerial
Wii Fit Trainer performs a Jackknife, bending back and then stretching upward with both arms and legs. This attack is the cornerstone of Wii Fit Trainer's combo game due to its combination of low knockback, low ending and landing lag, and 90° launch angle; especially if the move connects as Wii Fit Trainer lands, it can lead to heavy damage at almost any percent. Landing neutral aerial combos easily into virtually any attack at some percent range, but its most notable followups are up tilt, Header, up smash, another neutral aerial, and up aerial. At very low percents up tilt is one of the only moves fast enough to combo, and since up tilt is itself a combo move it often leads into another up tilt or at least puts Wii Fit Trainer in a good position to maintain pressure. From roughly 15% up to mid percents, Header is by far the best followup from neutral aerial due to its massive damage output. When Deep Breathing is active, Header can also lead into a forward aerial for even more damage. Up smash is another move that combos from low to mid percents for heavy damage, and at a specific percent range neutral air to up smash can even outright KO most characters if Deep Breathing is active. A second neutral aerial is the most all-purpose followup from a landing neutral aerial, since it has a few large percent window and still deals roughly 30% at the very least without counting any potential followups off of the second neutral aerial. Finally, up aerial is the move that combos out of neutral aerial at the latest percents, sometimes even leading to a kill.
Aside neutral aerial's huge combo potential when both hits of the attack connect, landing such that the opponent is only hit by the first part of the move comes with its own long list of followups, most taking the form of kill confirms since the first hit of neutral aerial has relatively low knockback even at higher percents. The most notable of these kill confirms is neutral aerial 1 to up smash, a combo that both works at a large percent range (with and without Deep Breathing) and kills extremely early thanks to up smash's immense strength. This kill confirm was further buffed in Update 8.0.0, since up smash's quicker startup time makes the combo both more forgiving to perform and sometimes kill earlier with extra time to charge the smash attack. At percents too late for up smash to connect, neutral aerial 1 to back aerial is the next most potent kill combo, working at virtually any percent. Similarly to the first hit of neutral aerial, landing only the second hit of the move creates much larger percent windows for the attack to confirm into both up smash and up air.
Aside from its excellent combo capabilities, neutral aerial is also one of Wii Fit Trainer's safest moves overall due to both its ability to cross up the opponent's shield and its aforementioned low landing lag, which results in the move being as little as -4 on shield. The move's only real weakness of note is its tendency to cause opponents to fall out of the attack entirely before the second hit connects in some situations, typically resulting in a dropped combo.