Smite the Monstrous destroys a targeted creature with a power of four or greater. In order for this spell to be cast, a legal target must be chosen. In other words, the creature must have a power of four or greater when Smite the Monstrous is cast.

Somewhat similarly, the targeted creature’s power must be four or greater when Smite the Monstrous resolves in order for this creature to be destroyed. If the power of the targeted creature is lowered to three or less in response, then Smite the Monstrous will become countered on resolution as it no longer has a legal target. For example, if a Kindercatch is targeted by Smite the Monstrous, the controller of the Kindercatch can target his own creature with Grasp of Darkness to lower the power of the Kindercatch to two, and therefore save his creature.