This is Freeza's main energy projectile instead of the more conventional Ki Blast.
The Death Wave is a projectile that travels across the ground, hitting low.
Upon impact, you can supercancel into any of his Supers.
The aerial version launches a small energy bullet down to the ground and upon touching the ground,
it will become the Death Wave
and travel across the ground as usual. When this Death Wave hits you can supercancel
like with the ground version, but you can't supercancel
when the initial air spark hits the opponent.
The EX version acts as a long-range launcher; when the Death Wave hits the opponent,
it explodes and launches them into the air. When you press up, Freeza will teleport next to them into the air,
allowing for your aircombo.
Note that for the aerial version, it will only launch with the actual Death Wave
and not with the initial air spark; that just knocks the opponent down.