Zero Suit Samus (SSBB)/Up aerial
Zero Suit Samus performs a fast flip kick upwards in midair. It has very quick startup coming out on frame 4, autocancels in a short hop, has low landing lag, and has a powerful sweetspot, being able to chain into itself at low to mid percentages while also having strong KO potential at high percentages, even being able to KO near the upper blast line at around 90%. This makes it a very potent juggling tool and KO option. Its utility is further aided by Zero Suit Samus' high jumps, which allows her to use the move to keep the opponent in the air for a long time. Its back hit even sends at a good trajectory that can combo into her back aerial.
Up aerial also has an interesting property: its clean hit lasts from frames 4 to 6, but on frame 5 and only frame 5, there is a very large sweetspot hitbox that appears in front of Zero Suit Samus, giving the move a deceptively large disjoint for an attack of its speed and strength.
Overall, it is one of Zero Suit Samus' most reliable KO options and one of her best moves overall due to its deadly combination of speed, power, juggling ability and disjointed range, and is a huge staple in her fantastic aerial and juggle game.
Hitbox 3 comes out only on frame 5.