Samus (SSB)/Back aerial
Samus performs an overhead kick behind her. The move is very fast coming out on frame 5 (being the second fastest back aerial behind Fox's) and it has good range. The move does not have a high amount of ending lag either although it does have moderately high landing lag if the move is not L-cancelled or auto-cancelled. It is the strongest back aerial in the game as while it deals below average damage for a back aerial only dealing 14% if the clean hit connects; it has extremely high knockback scaling (145 compared to 100). The move can KO Mario at 97% at the center of Dream Land and it can even KO him under 120% from one side of the stage to the other. Even the late hit is fairly powerful being able to KO Mario at 138% on Dream Land. Because of these factors, back aerial is one of Samus' most powerful and useful KO moves.
The move however can be difficult to land due to how floaty Samus is combined with her limited combo options. Samus' high short hop means that she cannot easily land it characters on the ground and Samus does not have many options to combo into the move at higher percents outside of down aerial. It is overall one of Samus' better aerials although the move's usefulness is limited due to Samus' attributes. The move also received a reduction to its knockback in the PAL versions not KOing Mario at the center of Dream Land until around 111% (155% for the late hit) making it a worse move overall in those versions.