Elemental HERO Thunder Giant [EHC2-EN004] Secret Rare

"Elemental HERO Sparkman" + "Elemental HERO Clayman"
Must be Fusion Summoned and cannot be Special Summoned by other ways. Once per turn: You can discard 1 card to target 1 face-up monster on the field with original ATK less than the ATK of this card; destroy that target.