Marth (SSBU)/Up special
Although relatively situational, Dolphin Slash is a highly rewarding move with a strong surprise factor if timed intelligently. The move's active hitboxes start on frame 5 where they hit the strongest and end on frame 10 where they are more disjointed but are much weaker. With its considerable disjoint, speed (faster than a grab), kill potential, and its frames of intangibility (frames 4-5 on the ground, 1-5 in the air), it is also Marth's best out of shield move but is his riskiest.
The move's biggest drawback is how punishable it is when whiffed. The slow falling speed afterwards as well as the move's landing lag leaves him wide open. It is safer to use on stages like Battlefield where he can land on the top platform if angled high.
As a recovery option, Dolphin Slash is considered subpar. Its speed makes it difficult to hit Marth out of without ledge intangibility and has a disjointed hitbox above Marth's head which can hit through the stage and punish people standing near the ledge. However the move doesn't travel far horizontally and, although it can be angled, the extra horizontal distanced gained often isn't enough.
As an edgeguarding option, Dolphin Slash can be used to punish opponents who ride the wall towards the ledge by testing their ability to tech. This is preferable to using a move such as forward air or back air for stage spiking, since Marth will almost always be at the ledge by the time the opponent is actionable after the stage tech, and can subsequently be hit by another back air. On the other hand, the player ProtoBanham opts to use a Dolphin Slash faced away from the ledge to try and swat opponents away. However, this requires Marth to be very close to the ledge, otherwise he may not grab it and fall into the blast line.
The move enables ledge grabs from the front starting on frame 8. It lacks a window for backward ledge grabs, so Marth cannot grab ledges from behind until a frame after the animation is over (frame 41 onward).