Roy (SSBU)/Side special
Roy performs a series of sword swings to form a natural combo, also known as a rekka. The player can input up or downward inputs while executing the move to perform different swings. This can be used to position the opponent in a manner that can confirm a sweetspotted 4th hit, which has high KO potential. The attack is notoriously powerful due to its amazing consistency, rarely dropping without the player making a huge mistake. The attack can carry opponents closer to the blast zone, improving the already high kill power. This is a particularly popular maneuver when used in tandem with neutral attack on Town and City. The sweetspots having higher hitbox priority also greatly assists with the move's consistent kill power. The lowered SDI and Hitlag multipliers are also crucial to its success, with the latter effectively increasing the already amazing input windows for the rekka. However, it does technically make it easier to SDI, albeit made worse by the lowered multipliers.
However, the attack does have issues, namely its extremely poor safety on shield. The lowest possible shield safety is -16 from an aerial hit, while the rest ranges from -29 (2nd neutral hit) to -46 (4th downward hit). In a similar manner to how neutral attacks work, however, Roy players tend to make use of the large input window for the multiple hits. This allows the player to bait out of shield options and get the rekka anyway. Considering mental frame data as a result of reaction time, the hits can effectively be safe. The low 4th hits can also be used to poke through damaged shields, which is improved by the extra shield damage that each hit of Double-Edge Dance deals; almost every hit deals some bonus shield damage.
The first hit can be used with wavebouncing for safe movement and mindgames, as well as crossing up opponents on shield. This can bolster Roy's approach, though the safety on shield makes it a bit difficult to use properly.
Hitbox Visual Table