anime punch flurry

You begin punching wildly at something within 20 feet of you, manifesting many fists. Roll 1d20 d4s, adding a d4 every time you roll a four, the target may make a dexterity save with a DC equal to 1d20 + your dexterity modifier, on a failed save they take the damage from each punch (d4), on a success they take half of the punches, the highest rolling ones. You then punch once more forcefully manifesting a much bigger fist doing as much damage as they would have taken previously on a failed save, there is a similar save for this but the target does it at disadvantage.