Heroes aren't always back and white, they have several shades of grey as well. Heroes usually embody heroism, known to have qualities such as nobility, bravery, selflessness, benevolence, forgiveness. Some (unusual) heroes may lack in a few of these traditional heroic qualities. However, they aren't villains either. They may be brave, but may not be benevolent and so on. These unusual heroes fight evil solely because they have a selfish motive behind it. There is no such thing as a 'selfless deed' in their world. Everything must be done for the sake of self-preservation. Such men and women are typically referred to as anti-heroes.
In the words of Deadpool from a rival universe, Marvel, "I may be super. I am definitely not a hero." In the DC universe, mercs, bounty hunters, sidekicks, vigilantes, etc. exist as anti-heroes. Here's our list for the most violent of them.
10 ARSENAL (ROY HARPER)
Roy Harper was originally Oliver Queen's sidekick, fondly known as Speedy. He possessed superhuman strength on account of being injected with Mirakuru, a Japanese serum made during World War II. He broke bad when he masqueraded as the Arrow and faked his death.
After leaving Team Arrow, he became Arsenal. He wasn't the same Speedy that fans knew. On account of his superhuman strength, he went on a bloody rampage against every enemy of his, like for example, the ones responsible for killing his daughter Lian Harper. In the New 52 retcon, Arsenal was a depressed alcoholic who was constantly misused by his mentor Green Arrow. He was sentenced to death for his war crimes by the end.
9 AMANDA WALLER
Amanda Waller, a government bureaucrat took to cold-blooded vengeance after she lost her husband and two children. There are two variations to Waller, a slender woman with a pixie cut and another, a short stout woman. Both these variations are ruthless women and master tacticians who anyhow get their job done.
After Amanda's personal tragedy, she left behind conventional crime-fighting methods. She worked endlessly as a bureaucrat and found a black-ops team called Task Force X. Waller eventually went on to form the Suicide Squad of incarcerated villains to fight crime. And when the Suicide Squad was set-up, things could be the same again.
8 JOHN CONSTANTINE
John Constantine is a sorcerer who relies on magic to gain favorable outcomes. Probably the most intriguing one in the list; theft, manipulation, lying, the use of his death wish, are some of the acts that define Constantine.
So, why's he a hero after all? Because his motives are still doubted. It's not clear if John takes to sorcery to just seek revenge or to selflessly deliver justice when all else fails. John's exorcism will never come without fatal consequences. John's conscience has known to suffer in the process.
7 JASON TODD (RED HOOD)
When fans couldn't take Jason Todd's retcon anymore, DC decided to conduct a call-in vote to determine his fate. In Batman: A Death In The Family (1988), the Clown Prince of Crime killed Jason Todd with a crowbar.
Decades later, in Red Hood (2005), Jason Todd was resurrected as a vengeance-seeking anti-hero. Brought back to life as Red Hood, Jason Todd went into an all-out revenge-seeking campaign against his enemies. His days of Robin vigilantism were far over, and this Todd would employ lethal force. Apparently his mind had suffered in the resurrection process and he was hinged by the fact that Batman let Robin live.
6 DEADSHOT
Deadshot started out his career as a Batman antagonist. Deadshot suffered years of childhood abuse by his father, until one day he decided he had enough. Intending to kill his father, Deadshot accidentally shot his brother. And that was that.
Deadshot worked to become the finest gun for hire there ever was. Not only did he join Amanda Waller's gang of incarcerated supervillains, but he also helmed the Suicide Squad with aplomb. He was rewritten in The Man Who Replaced Batman as a new savior of Gotham city. With a mission to upstage Batman and also to become Gotham's number 1 crime fighter, Deadshot's morality confuses an average fan.
5 THE COMEDIAN
Edward Blake aka The Comedian is known to deliver his own brand of justice. He's a vigilante in the strictest sense of the word. He's fought crime for the longest duration. His name first appeared in Watchmen #1 (1986) as a government-sponsored vigilante, Comedian.
A crimebuster and a molester, The Comedian is your standard anti-hero. He attempted to rape Silk Spectre backstage during one of their gigs. Later, in the 1960s, he joined Crimebusters with the intention of fighting crime but set everything on fire during their very first meet!
4 JONAH HEX
Ah Jonah Hex from the wild wild west. Sold as a slave in childhood, Jonah Hex made his first appearance in Earth-One as a bounty Hunter. His exceptional talent as a sniper came in handy in the American Civil War. Jonah joined the Confederate States Army and quickly rose through the ranks. A loner and hideously disfigured, people didn't want to mess with the likes of Jonah.
However, just as any anti-hero, Jonah's dilly-dallying morality played its part. Jonah oftentimes found it difficult to go on a murder spree. Like for example, he surrendered to the Union Army during the American Civil War. Jonah's conscience didn't let him fight the abolitionist, those seeking to end slavery.
3 BLACK ADAM
Mighty Adam aka Teth-Adam was created by the wizard Shazam in ancient Egypt. Originally meant to be a savior of humanity, he quickly corrupted. As a result, Shazam imprisoned him and renamed him, Black Adam.
Black Adam returned in the modern-day as the ruler of Kahndaq. Having spent time with both the Justice and the Injustice society, Black Adam chose his own brand of justice. He believes he is the beholder of righteousness. Hence his means justify his ends. Black Adam has mercilessly orchestrated murder sprees against his enemies.
2 BATMAN
Generally considered as a hero, Batman does act like an anti-hero from time to time. Frank Miller's The Dark Knight Returns is one example, to begin with. To start off with, he's broken his "no-kill" rule many times, particularly in his early days. In Zack Snyder's Batman v Superman, Batman was shown as a standard anti-hero. This rendition of Batman was lethal as he ran over his enemies. And it is just one of the many lethal Batman renditions.
Batman breaks rules from time to time, he's avenged Damian Wayne's death by killing the Heretic, he bombed a monastery in Batman Begins and so forth. He may 'refrain' from using guns, but if need be, he will go to the extent of hanging a mental patient from his helicopter.
1 HARLEY QUINN
What can be said about Harley Quinn who ever since her retcon has had an ambiguous relationship with morality? Pre-52 Harley joined teams with Joker and furthered his terror mayhem far and wide.
In the New 52, Harley emerged as an anti-heroine fighting for the law. Fans may not have always agreed with Harley's anti-heroine avatar. But the way she confronted the Joker in #52 and aided the Suicide Squad proved her redemption arc was a success. Who knows, someday Harley could emerge as a hero in her own right.