While Evil Versus Evil may be fun, it carries the risk of Darkness-Induced Audience Apathy. People just DO like having someone to cheer for. But if both sides are equally reprehensible, there's really no point to it. Or maybe the villain is such a Magnificent Bastard with many a Crowning Moment of Awesome (or generally just damn cool) that it's way easier to side with them. Especially when their enemy is an Eldritch Abomination, Complete Monster or somesuch. If they shoot way over the line, the character in question may end up doing a Heel Face Turn. Examples of A Lighter Shade of Black include: