This is literally exactly the same as casting a curse. The three fold law is Wiccan dogma not a law of physics, so there is not bad karma for cursing. This is not even how karma works. Stop being holier then thou!
Someone in your life giving you a rough time? Sweeten them up a bit: Write the persons name on a piece of paper, roll it up, and stick it in a bowl of sugar, Hold your hands over and say: By sugar and spice and everything nice may sweetness last by this
Full Moon Oil: Mix prior to the full moon. Charge under the full moon in a clear jar. Use to anoint candles for rituals or for use on yourself when you need the moon's energy.