Elemental HERO Thunder Giant (Quarter Century Secret Rare) (RA03-EN153) - Quarter Century Bonanza 1st Edition

"Elemental HERO Sparkman" + "Elemental HERO Clayman"
Must be Fusion Summoned. Once per turn: You can discard 1 card, then target 1 monster on the field with original ATK less than the ATK of this card; destroy that target.