There are a few attacks in the Smash Bros. series that cause the reverse effect. Characters that are struck by these attacks are forcibly turned around to face the opposite direction instead of flinching. While the reverse effect does not naturally reflect projectiles, most moves with it are also reflectors.
While hitboxes with the reverse effect generally do not cause knockback, there are situations where they can boost the momentum of an airborne character.
Reverse effect now forces characters with mirrored stance to turn away from the screen and show their back side. This makes it the only way to see the back side of characters with mirrored stance.
List of reverse attacks