Gut Check (move)
From the Super Mario Wiki
Gut Check (formerly known as Stomach Attack) is King K. Rool's down special move in Super Smash Bros. Ultimate. For the attack, King K. Rool protrudes his stomach towards the opponent, countering an attack back at the opponent for extra damage, but unchanged knockback. Gut Check is also a reflector, due to its ability to reflect projectiles. The counter hitbox is only on King K. Rool's belly, rendering the rest of him vulnerable to attacks. However, this issue can be mitigated somewhat, if the player tilts the control stick before K. Rool protrudes his belly, allowing him to counterattack opponents behind him.