So one really specific idea that I like and that fits quite well here is getting high damage creature removal. isn't supposed to get, say, "~ deals 13 damage to target creature" because once the number is higher than the vast majority of creatures' toughness, it's just a murder, which is and blurs the line between the two colours. Since there's no place for these dumb big number removal spells in either colour, I thought they would be a good fit in Rakdos, which feels like the right place for that sort of overkill feeling. Though the cmc and rarity here retrict the power level somewhat, so the result was this.
Indiscriminate Hate Sorcery Indiscriminate Hate deals 5 damage to target creature. “Astaroth does not pick favourites, and he does not hold grudges. If you find yourself suffering by his hand, then he is simply having a bad day, and you are simply having a worse one.” —Dumien, Astaroth cultist