Not all fictional heroes are the sort of person you might expect to be a hero of a story. The idea that there is an "Ideal Hero" and there are "antiheroes" who deviate from the ideal has been around since classical antiquity if not earlier. Since then, writers have explored many types of antiheroes, each of which lack one or more traits of an Ideal Hero.
An Unscrupulous Hero is an antihero who lacks the moral character of an Ideal Hero, but is A Lighter Shade of Grey than the antagonists.
Despite this, these heroes share one overriding heroic trait: unlike a Nominal Hero, they are heroes in the true sense of the word: when they have to take a stand on one side or another, they choose to fight for good for a morally positive reason, and aren't just helping the heroes for selfish reasons.
These characters generally fall under two different categories:
They are defined by dark experiences that have made them cold and cynical, and due to the settings in which they exist, there will usually be no compunctions to using more extreme methods. They are as much about payback (or any assorted type of catharsis) as they are the greater good, and their targets will be deserving of it, more likely than not. Just don't expect them to be mindful of any collateral damage.
They may be a little more selfish, but unlike a Nominal Hero, have a much stronger honor code that keeps them from becoming less sympathetic.
In Death Note we have L, the Hero Antagonist to Light/Kira'sVillain Protagonist. While L does try to capture Kira because he's a murderer, his main motivation is because he sees Kira as a challenge, and it's revealed that in general he only cares about cases he finds interesting, making him a Nominal Hero too in this regard. Describing himself as "childish and hates losing," he is willing to resort to, among other things, kidnapping, torture, lying and invasion of privacy to get the job done. The series lampshades how Not So Different he and Light are from each other fairly often. Still, L only reserves his justice for people he sees as evil, and to be fair his accusations seem to always be correct. Moreover, while L does order the deaths of a few criminals to help further the investigation, these criminals were on death row anyway.
There's also his successor Near who teeters between this and Nominal Hero. His other successor Mello is a full-stop Nominal Hero, though.
Hellsing has several of these, but the most prominent example is FatherAlexander Anderson. He specifically targets vampires and heathens, believing them to be an affront against God and danger to the innocents of the world. Which they are. He takes it a little too far sometimes with his Ax-Crazy attacks and Blood Knight beliefs, but he also adores children, acts like a surrogate father to his Iscariot followers, respects Integra's principles and Nerves of Steel attitude, and takes a stand against Maxwell when he starts killing the innocent survivors of Protestant England.
Another mention goes to Anderson's Iscariot followers, most of whom he raised himself. Compared to Maxwell and his fanatical Holy Crusaders, Heinkel, Yumie, and the rest of Iscariot are under Anderson's Even Antagonists Have Standards direct influence, which prevents them from committing similar atrocities against innocent but non-Catholic populations.
Scrooge McDuck develops into one by the "Empire Builder From Calisota" chapter of The Life and Times of Scrooge McDuck. His life experiences have hardened him to the point that he's become a corrupt robber baron, he hates his family, and only derives joy from getting even richer. He remains a good guy only because of his brief but ignored epiphany moments. He isn't redeemed by his family until later on.
Disney Italy has Paperinik the Devilish Avenger. He is Donald's superhero (sort of) alter ego, but Donald initially created it to avenge himself against torts (real or imagined) he suffered, his main reason to fight criminals is that crime in general piss him off (assuming they didn't somehow target Donald or Paperinik in the first place), and even the most light-hearted stories have him doing things like sick a lynch mob on the Beagle Boys (they had organized a marathon with Paperinik's Secret Identity as the prize to empty Duckburg and sack it. Once he found out they didn't actually know his real identity, Paperinik lured the citizens back in town and had them catch the BB in the act).
The Blues Brothers, especially Jake. They mean well enough as they just want to save the orphanage they grew up in, but they're not above scamming patrons, acting like jackasses and endangering bystanders more than they really need to.
James Bond in Licence to Kill, as he ditches MI6 to take down drug lord Franz Sanchez and avenge Felix Leiter. As part of his Roaring Rampage of Revenge he kills off quite a few bad guys in particularly terrible ways, like feeding someone to sharks and shoving another down a stone grinder.
Sheriff Matt Morgan from Last Train from Gun Hill is simply trying to execute his duty to the law; however, he has no qualms about threatening his former friend's son, whom he's captured and holding for rape and murder, among other dirty tricks.
Despite being a straight up bad guy in the films, in the novel Denethor of The Lord of the Rings starts off as a wise ruler dedicated to protecting his kingdom, though he treats his allies with suspicion and verbally abuses his son. Eventually the combined stress of Faramir's coma and his despair send him Jumping Off the Slippery Slope.
Mr. Slippery from Vernor Vinge's novella, "True Names", is an out-and-out criminal hacker, in it for the fun, but when the chips are down, and the world needs saving, he's willing to save it. And not just because Federal agents have made him a deal he can't refuse—though that certainly removes any lingering doubts he might have had.
Harry Dresden, despite being one of the best examples of Chronic Hero Syndrome you'll ever encounter, is not at all unwilling to get his hands dirty, and though he may have a My God, What Have I Done? afterwards, it doesn't stop him doing it again. This comes to a head in Changes when he agrees to become the Winter Knight in order to save his daughter, despite knowing that he would then be totally at the command of a manipulative and utterly ruthless Faerie Queen who could then make him do anything.
Felix Harrowgate of Doctrine of Labyrinths is a wizard uses his powers to put the dead to rest, save a country from invasion, and take out Magitek machines before they can annihilate another country, all at considerable risk to himself. Unfortunately, he also says horribly cruel things for the sheer joy of it, repeatedly mind-rapes people including his own brother, and has a rage blackout in which he seriously crosses the line with an anonymous sex partner.
Thomas Cromwell is portrayed as this in Wolf Hall, with a very colourful past, and being quite willing to abuse the system to have his enemies executed.
In The Fire Rose, Jason Cameron is pretty amoral. To the extent that he's a good person, it's because he takes Cut Lex Luthor a Check and Pragmatic Villainy so far that they take him out of the "villain" sphere entirely; he's a philanthropist because that (used to) earn him street cred in his social circle, and because a well-fed proletariat work well and don't start riots. Likewise, he's known for fair business dealings because he doesn't need to do anything shady, but he doesn't especially care that his apprentice and agent gets his rocks off on rape and uses his magic to rig cockfights, except that they show him to be a complete tool and unfit to be a Master. He does develop genuine feelings of love for Rose by the end, though.
Pocket in Christopher Moore's Pocket the Fool novels. He is deeply cynical, sarcastic and bitter due to his childhood as an orphan and generally being treated like a slave by his master King Lear. However he is protective of Cordeliawhom he genuinely loves and has a sense of justice when it comes to other oppressed groups. That the latter also tends to go along with his acute sense of vengeance he finds very convenient.
24: Gives us Jack Bauer, Probably the most famous unscrupulous hero in popular culture.
Blake's 7: Avon probably averages out here, especially in series 1 and 3 where he's amoral enough to try and abandon Blake on a Hellhole planet but occasionally shows concern for the others, especially Cally. In series 2 he has enough Pet the Dog moments to push him closer to Good Is Not Nice, but by the final series the stress of maintaining a rebellion he wants nothing to do with turns him into a Nominal Hero.
Revolution: Miles Matheson after the blackout became this. He helped to start a dictatorship because he wanted to bring peace and order, as shown in flashbacks in episode 3. However, he became the Butcher of Baltimore, hurt Rachel (shown in flashbacks of episode 17), and handed Alec over to the Texans when Alec balked at assassinating the Texan president (shown in flashbacks of episode 14). He ended up leaving the Monroe Republic when Monroe went too far and Miles failed to assassinate him (elaborated on in the first season finale). He makes it clear to Charlie that he hurts people and he doesn't think twice about it. Later on, Charlie's influence causes him to become more of a Pragmatic Hero.
Tsukasa Kadoya, the main character of Kamen Rider Decade, is held in prophecy to be the Destroyer of Worlds, who will bring about an end to the Rider multiverse and kill all the Kamen Riders. He acts less "ultimate evil", however, and more "kind ofa tool" - he will troll and endanger other people to find and defeat the bad guys of the fortnight, although he'll throw himself into the firing line as well. Much of the series' mystery is "Is Tsukasa a Jerk with a Heart of Gold, or actually the ultimate evil?"
Breaking Bad has Hank Schrader become one in Season 5B. He spends that entire season trying to bring Walter White down, who by this point has become a monster. However Hank's tactics to do so range from the morally questionable to downright illegal. He even at one point flat out says that, if a plan involving a cooperative Jesse should go wrong, that he doesn't care if Jesse gets killed.
Team Fortress 2's malevolent mercs (and long-suffering P.A. Miss Pauling) may not have consciences, but they are capable of human affection, which is more than their ironically named business rival, Gray Mann, can say...
The Third Street Saints have become this by the time Saints Row IV rolls around.
Sarah Kerrigan in StarCraft II. She's no longer the Villain Protagonist she was in Brood War, thanks to being freed from the Overmind's programming, but she's still capable of controlling a Horde of Alien Locusts by force and chooses to use them to kill Emperor Mengsk, mainly for personal revenge. She can be persuaded to give civilians a chance to get out of her way, but she really had to think about it first.
Ammon Jerro of Neverwinter Nights 2 is literally Hell-bent on saving the Sword Coast from the King ofShadows at all costs. He goes so far as to stealing the most sacred relic of a extraplanar race of Holy warriors, making several infernal pacts with various demons and devils of the lower hells, killing any who oppose him (knowingly or not), abandoning any allies if they do not pull their weight, and even razing entire villages if it means he has a better shot at defeating the King of Shadows. He's even the Disk One Final Boss. That is until he joins you anyways.
Midna in The Legend of Zelda: Twilight Princess may be this, especially at the beginning. Even when she had no sympathy for those who lived in the light, she still fought for a righteous cause. She loves the people under her rule and wanted to save them. Plus, her dispassion for the people of Hyrule is no different from a government's lack of interests in another nation's politics. She may not have cared about saving the world of light (at the time) but she sure as hell didn't want to worsen the situation either.
Zevran from Dragon Age: Origins qualifies, if the player can gain his loyalty. He can be recruited after he tries to kill you; he swears to help you end the Blight if you spare him. He advocates the use of poison, rather enjoys his profession and is one of your more morally ambiguous companions. With that in mind, he is also fiercely loyal to your PC if you can get his affection high enough and is nowhere near as bad as his former employers, theAntivanCrows.
The player character can be played as an Unscrupulous Hero. You can lie, extort, steal and murder your way through Ferelden, all in the name of stopping the Blight (or For the Evulz, depending on the player). Given that you are the only thing standing between Thedas and total annihilation via darkspawn, anything goes.
Castlevania: Lords of Shadow 2 is mainly about Dracula's development from a Nominal Hero, who is only 'good' because he's fighting SATAN, into one of these. Admittedly not much of a jump, as although he does get some Pet the Dog moments regarding his family, he never stops being utterly ruthless, and the mountain of tragedy he's gone through over the centuries never leaves him entirely. The main development is that while his desire for vengeance on Satan and Zobek certainly remains at the forefront of his motivations, it becomes clear as the game goes on he really just wants to be at peace with his family, and in the end, Marie and Alucard forgive him and help him find his peace.
Celesto Morgan, of Dominic Deegan, is the appointed Champion of Chaos and Destruction. While he views himself as a champion of freedom and destroyer of tyranny and evil, his actions frequently show him to be almost as destructive as the things he fights, such as his battle with The Infernomancer in Lynn's Brook, in which he killed more people than the man he was there to stop. He has also been the vigilante executioner of two, up until that point Karma Houdinis in the story and has become He Who Fights Monsters against the Beast.
Worm gives us Armsmaster, who arranges the death of multiple "villains", including a fifteen-year-old girl he knew to be The Mole, in order to give himself a chance to defeat Leviathan in a one-on-one fight.
In El Tigre, although Manuel Rivera is usually on the good guys side, that doesn't stop him from doing mischevious things from time to time.
In Tom and Jerry, although Jerry is generally a Friend to All Living Things, he's definitely not above using violence for reasons other than self - defense or protecting others, often as vengeance for a legitimate wrong, but occasionally, because he's bored. Often when his actions are unambiguously unheroic, especially when unprovoked, we get a rare Laser-Guided Karma victory for Tom.