Marth (SSBU)/Down special
Marth's down special move in Super Smash Bros. Ultimate is Counter. If the opponent hits Marth with an attack at the correct moment, Marth will throw out a counterattack. While this can be used as a surprise move in certain situations, it is usually rather punishable and easy to whiff. It also doesn't grant much followup ability if it does hit, making it a rather rarely-used move in competitive play.
It can gimp certain recoveries, such as Screw Attack, Fire Fox, and Fire Bird as their active hitboxes can trigger the counterattack. Some moves may also move the opponent too quickly, such as Sephiroth, whose uncharged up special places him past Marth before he can counterattack. In this scenario, a turnaround Counter can be used.
The move's true base damage is equal to 1.2× of the countered attack's damage, with a minimum of 8% and a maximum of 50%. Additionally, the hitboxes ignore any kind of armor, and they play an additional sound effect on hit if an attack that deals at least 13% is countered, which is shared with Marth's Final Smash.
Upon countering an attack, Marth immediately transitions to the first frame of this state, in which he freezes for 21 frames alongside the opponent before the counterattack proceeds.