Mewtwo (SSBU)/Forward aerial
Mewtwo slashes the air with an energy-infused swipe. Considered one of the best tools on Mewtwo's moveset as well as one of the best moves of its kind in the game, forward aerial plays multiple important roles in Mewtwo's kit. It is able to start combos, while also serving as an effective poking tool with its somewhat disjointed hitbox, low landing lag and shield safety (-3 on shield if landed properly) and as a kill option at higher percentages. It also boasts 7 frames of start-up, tying it with neutral aerial for having the lowest start-up of Mewtwo's aerials.
Notably, forward aerial becomes an near-inescapable follow-up if Mewtwo is able to land an aerial Confusion on opponents who have accumulated at least 140% in damage and lacks a frame 1 combo breaker. Against certain characters it starts being true earlier depending on their airdodge speed and/or the speed of their fastest aerial/escape option.