When you use dair and it hits the ground, it has a shockwave effect and pushes enemies away from you and damages them a little (It doesn't stop what they're doing, just like Fludd) It also works on people RIGHT below you (Land on a platform)
It's just an OK thing I found, not too great, but it's helped before, and even gave me a free smash one time
It's just an OK thing I found, not too great, but it's helped before, and even gave me a free smash one time