Luigi (SSBU)/Down special
Luigi swiftly spins and creates a multi-hit damaging whirlwind that launches opponents with its final hit. Unlike previous games, it no longer gains sufficient height even with button mashing, making it essentially useless for recovery, and makes Luigi easier to edgeguard and gimp. However, the move has gained some notable strengths. It has larger hitboxes and now has a windbox that sucks the opponent into the move which helps it connect with opponents more consistently. It also has increased damage and knockback, making it a viable KO move particularily near the upper blast lines, and can be combo'd into from his down throw for a potential KO at high percents. It can also be a KO move on the ground near the ledge at very high percents, especially if the opponents' DI is poor.
It also has one last notable strength which is that it grants Luigi invincibility frames during the move. The amount and duration of invincibility depends on whether the move is used in the air or on the ground with the move having invincibility on frames 4-8 if used on the ground and frames 1-7 if used in the air. With its new trait of invincibility, Luigi can potentially break out of combos and tank through an opposing attack which when used properly, can help him get out of disadvantage and launch a counterattack. Lastly, its strong damage and knockback synergize with its invincibility to give it great ledge coverage use.
Overall, despite losing all of its recovery potential, the move has excellent utility as a KO move, combo and disadvantage breaker, and ledge coverage tool, making it one of the most useful moves in Luigi's kit. However, its effectiveness in combo and disadvantage breaking have led it to be overused by many players which has caused the move to be very easy to read. Therefore, players must remain unpredictable and mix things up in order to take advantage of its strengths.