Dragon Fist

You unleash a serpentine draconic spirit that coils through the
air and lashes out at every creature of your choice within a
60-foot cone originating from you. The targets must make a
Strength saving throw. On a failed save, they take 2d8 radiant
damage and are knocked prone. On a successful save, they
take half as much damage and are not knocked prone. When
you cast this spell, choose one creature within the cone to be
the target of the spirit. If this creature fails their saving throw,
they take an additional 12d6 piercing damage and are
subjected to a second effect as the dragon rushes forward and
strikes them with legendary power.
Rush. If the target is Large or smaller, they are pushed up to
100 feet away from you in a straight line. If the target strikes a
surface, both the surface and the creature take 1d6
bludgeoning damage for every 10 feet the target was pushed.
If the surface were to break, the dragon continues beyond the
surface and the damage resets.
Explosion. If the target is huge or larger, the spirit entangles
them and implodes into a devastating wave of radiant energy.
The target immediately takes 6d6 radiant damage, or 8d6 if
they are gargantuan.