A Lighter Shade of Black

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.

So that's where this trope kicks in. It basically means that the author is clearly trying to portray one side of the conflict as the better or more symphathetic one, so the audience can root for them. Since both sides are supposed to be villains, this isn't that hard. You just need to give your Lighter Black a little edge on the sympathy meter. The idea is to have the audience say "Yeah, Alice may be evil, but at least she's not half as bad as Bob!"

This can be done in many ways. Give your villain the Sympathetic POV. Have them Pet the Dog, be a Noble Demon or invoke Even Evil Has Standards. Perhaps they're simply a smaller threat to the world. Maybe their goals are, or used to be, somewhat sympathetic. Maybe they have many Evil Virtues. Or, when compared to the opposition, their cause still seems a little more "right" or their character "pure" than that of the enemy. Since we want them to win, this may lead to a villainous version of Right Makes Might and Pure Is Not Good.

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.

See also A Lighter Shade of Grey, Nominal Hero, and Shades of Conflict.

Comic Books

 * In Wanted, Wesley and his allies are ever so slightly better than their opponents, which makes it possible to root for them.
 * Marshal Law; the title character is supposed to hunt and kill "super-heroes" (who are, in truth, nothing of the sort) but has only slightly better morals and ethics than they do. Not that he cares, should anyone point it out.

Tabletop Games

 * This is what Warhammer 40,000 has instead of Good versus Evil, and is presumably what fans of the Lighter Black factions (Tau, Eldar, the Imperium) see in playing on the side of such horrible people; they're fighting against the very incarnations of death, savagery, consumption and, well, Chaos.

Theatre

 * Sweeney Todd is a murderous barber who slashes his customers' throats and has them baked into pies. But in Sweeney Todd: The Demon Barber of Fleet Street, we root for him because he wants revenge against the corrupt judge who falsely transported him for life in order to get at his beautiful wife, as well as having some rather skeevy designs on his daughter when she comes of age.

Video Games

 * Fate Stay Night: Part of Heaven's Feel seems to be solely dedicated to making the players like Kotomine more, with several Enemy Mine and Pet the Dog situations and most importantly, an utterly epic fight where he holds his own against Complete Monster Matou Zoken and his Servant quite well.
 * This is tied in to the point of that route and arguably to one of the overarching points of the entire game as well. FSN's three routes take different approaches to morality as seen through the eyes of the main character; in Fate, Kotomine is portrayed as a fairly simplistic Complete Monster with no motives beyond Evil Feels Good, and in Unlimited Blade Works he takes a backseat to the conflict between Shirou and Archer. Only Heaven's Feel fleshes him out at all, but in doing so it makes him into a much more complex character than when he was portrayed in simple black and white terms.
 * Knights of the Old Republic 2: In the Darkside Ending, Kreia will say that the PC is not a Sith. Not really. Presumably, she considers them a Dark Jedi instead, i.e. someone who uses the Dark Side for their own advancement rather than submitting to the Sith Code and philosophies.
 * This is the case in the first Disgaea game (Laharl the wannabe Evil Overlord vs. an Omnicidal Maniac). The second and fourth have more heroic protagonists while the third is mixed (Mao wants to slay his father, the Overlord, for trivial reasons and the rest of the cast have more heroic goals
 * Blood has no good guys. On one hand you have a cult trying to summon a dark god, murdering anyone they want to and experimenting on the rest. On the other side you have one of their failed projects, a sadistic revenant named Caleb who was one of those cultists and also is murdering anyone he feels like. At least Caleb is fighting to avenge his wife  and has a sense of humor.
 * The Scarlet Crusade vs the Scourge in World of Warcraft..
 * God of War is full of this. Yeah Zeus pulled a humungous dick move by, but this was mostly because Kratos . He was pretty much causing as many wars, if not more, than the very asshole he killed because he was supposedly the lesser of 2 evils.  , so Ares is another example to Kratos. On top of that Kratos basically   You can even kill as many innocents as you like along the way, some even REQUIRED to be killed in torturous ways just to solve puzzles. But it's ok because,

Web Comics

 * Lackadaisy is about a gang war between two rival booze-smuggling organizations, the eponymous Lackadaisy and the Marigold, during the Prohibition. What sets the rivals apart is that the Lackadaisy is mostly a bunch of underdogs who were seduced by the gang when it was at its prime and remained stuck there or couldn't get a job elsewhere, and the Marigold gang is a group of experienced and hardened criminals who seem to enjoy their job more than they should and have very few (if any) redeeming qualities.