Ruthless Means (SGX3-ENS01) - Speed Duel GX: Duelists of Shadows 1st Edition

Once per Duel, during your Main Phase, if you control an "Evil HERO" monster, you can discard 1 card to make 1 face-up monster your opponent controls lose ATK equal to its own DEF, or lose DEF equal to its own ATK (your choice).