Joker

The Joker is one of the numerous major villains from the DC Comics.

The Joker, Clown Prince of Crime, is Batman's arch-nemesis. An agent of chaos known for his malicious plots, wacky gadgets and insidious smile, he has caused Batman more suffering than any other villain he has ever faced. His origin, name, and true motivations remain a mystery.

Personality
In the mini-series Underworld Unleashed, the Trickster remarked, "When super-villains want to scare each other, they tell Joker stories". As far as truth about Joker's personality, one word sums him up… unpredictable. One day The Joker may be a harmless clown, on others he can become a crazed super-killer.

With the conclusion of Infinite Crisis, the Joker cruelly murdered the once-hero now villain of the comic, Alexander Luthor, Jr. who was a mirror opposite of Lex Luthor. Alexander Luthor set up a Secret Society of Super-Villains aimed at taking down Superman, Wonder Woman and Batman, however he made the deadly mistake of not inviting the Joker. One night Alexander Luthor was trapped by Lex Luthor and the Joker in an alley. The Joker attacked Alexander with an over-powered joy buzzer, which horribly burnt one side of his face. Lex Luthor watched on as the Joker shot Alexander from point blank range with a shotgun, killing him instantly.

In addition to this The Joker is one of the few villains attributed with killing one of Batman's sidekicks, the other being Black Mask. The Joker beat Jason Todd to death in the comic "A Death in the Family". For any Batman villain, killing a Robin is almost the peak of villainy. Only two Robin's and one Batgirl have ever been maimed or killed at the hands of super-villains.

Insanity
The Joker's insanity appeared to be a strange mixture of violently aggressive psychopathy, nihilism, and fixated narcissism. He was frequently shown to have no regard for human life, and treated the pain and suffering of others as personal sport.

While frequent attempts had been made to diagnose the Joker's 'insanity', none were consistently proven successful. Every attempt to cure him had proven completely fruitless, as the Joker actively and energetically resisted separation from his madness. He spent the majority of his time in Arkham Asylum, a somewhat inadequate facility which he and other inmates came to view as sort of a home. The Joker was able to escape from the Asylum almost at will, and did so disturbingly frequently. He treated it like a resting place between his criminal exploits.

During the events of "Arkham Asylum: A Serious House on Serious Earth", it was hypothesized by Arkham psychologists that the Joker actually existed in a state of almost "super-sanity". It was speculated that he redefined his own personality every day. This explained why he sometimes acted as a horribly sadistic lunatic one day, while being a simple mischievous clown the next.

One person who still saw some humanity in the Joker was the Martian Manhunter. When the Joker gained the Philosopher's Stone and tried to create chaos on Earth, J'onn was able to order the Joker's mind and cause temporary sanity, where the Joker expressed regret and remorse for his actions, and became desperate for a means to make up for them.

In his transformation after his deformity, Joker adopted a much more sinister personality, no longer telling jokes the way he formerly did. However due to the Joker's nature of altering his personality, he abandoned this new personality from time to time.

Day of Judgment featured Martian Manhunter taking the Spectre into the Joker's mind, along with the rest of the Justice League. He was attempting to show the Spirit of Vengeance that there was decency and humanity even in the most corrupted and evil of souls. Although most of Joker's mind was a horrible twisted hellish place full of demons, deep down, at its heart, there is a kindly couple living in a small domicile separate from all of the anger and torment. This revelation proved that there is some good to be found in all people.

Abilities
Due to his mental state, the Joker is immune to fear as he does not understand the concept and sees everything as a joke. He also has an immunity to poison due to prolonged exposure to chemicals. The Scarecrow's fear gas has no effect on him, and Visionary failed to hypnotize him into a state of fear in Birds of Prey #121. He and Poison Ivy have shown immunity to each others' chemicals. As well, the Harlequin of Hate also possesses a very high tolerance for pain. In Birds of Prey #16, the Joker was in a leg cast, but jumbled about as if it was not even there. He has laughed after being shot in Batman: Dark Victory. He showed no symptoms of pain after a couple of batarangs slit his mouth in Batman Confidential. Most of the time, he seems to enjoy pain, provoking others to take a swing at him; thus, he may, with some truth, be accurately described as a sadomasochist. Bullets seem to do little more than slow him down or put him out of commission temporarily. On several occasions, he has been known to survive explosions and crashes. His bones heal quickly, and it has been hinted in a few comics that he does not physically age.

The Joker is a genius inventor and chemist. Using a seemingly laughable but actually very dangerous and deadly arsenal of comedy-themed weapons, such as his patented laughing gas, a bang-labeled spear-gun, explosive whoopie-cushions, an acid-squirting flower, a high-voltage joy buzzer, razor-sharp cards, poisonous pies, acid spraying water gun, and exploding cigars. He has managed to create an MO which fits his macabre appearance. The Joker is immune to his own venom as well as various similar toxins. The Joker is an excellent marksman, as shown in the story arc "Lovers and Madmen". He has made accurate head shots on his victims and never missed once; he also demonstrated his accuracy to people in order to get hired for his skills by throwing a deck of playing cards in the air and shot a jack and both joker cards. His accuracy has also been proven when he shot the ropes of hostages he had hanging from a building to distract Batman. The Joker has occasionally demonstrated above average and noticeable hand to hand combat skills, having caught Batman off guard with a kick on some occasions with being and adept brawler even though he doesn't have any specific fighting style, he used street fighting techniques. He has shown to be adept with non-comedy themed weapons such as guns, knives, explosives, and even such seemingly non-lethal items as a pencil.

In “A Clown at Midnight” and again in Batman #663, there is a panel in which the Joker is sitting in a cell at Arkham waiting for the Dark Knight’s arrival. As he waits, a mosquito lands on his unnaturally pale arms and attempts to suck his blood. The insect dies quickly instead, for the Joker's bloodstream acts like a poison, killing off its unknowing prey.

The Joker does not possess any outright super-human powers; however, he does show several inhuman abilities. The Arkham Asylum story arc suggests that he is "super-sane;" this means that he sees how the universe really is, without any personal illusions, and that his entire personality can alter to fit the circumstances, making him excellent at impersonating and lying as he truly believes what he says. He has the great strength that madmen are often said to have, and is quite agile. And, like so many comic book characters, the Joker always has the habit of cheating death. People have repeatedly assumed him dead, only for him to rise up again and wreak havoc once more.

It is debatable if it classifies as a super power or not, but the Joker's insanity, or his frame of mind, leaves him immune to the Spectre's judgement, though warranted, as Batman explained once that the Joker doesn't actually know what is right and wrong, a crucial understanding the Spectre needs to judge. In a way, one has to know one's deeds are evil or wrong for the Spectre to judge, and the Joker doesn't. Also, both Jim Corrigan and Hal Jordan Spectres have had major problems with navigating the Joker's mind, Corrigan even managed to get lost in it and Jordan literally was blasted out of his boots to the moon when he tried.

The Joker also has the tendency to break the fourth wall and seems to have a heightened sense of awareness that he is a comic book character. He is the only character to talk directly to the reader and has the ability to do things such as "turn" the comic page or handle his own word balloons. The Joker also seems to know that he exists as Batman's perfect foil. In " Going Sane" (in Legends of the Dark Knight #65-68), the Joker, thinking that he has killed Batman, figures there is no point to him being the Joker anymore and gets plastic surgery and attempts to lead a normal, sane life. However, upon discovering that Batman is still alive, he reverts to insanity and continues his life as a mass murderer.

Regardless of whether he is insane or faking insanity, his intelligence is obvious and his malevolence unmatched. The villains of Arkham fear and sometimes take orders from him, and those who do not know any better and shrug him off as a clown soon discover him to be a force to be reckoned with. He has a habit of pushing his authority and does not always use henchmen to enforce it. Some notable weight-pushing, leadership, and rogue bossing can be found in Arkham Asylum: ASHoSE, Salvation Run, Batman R.I.P., Emperor Joker, & Batman: Gotham Knights.

Trivia

 * Nicknames for the character include The Clown Prince of Crime, The Thin White Duke of Death, The Harlequin of Hate, The Ace of Knaves, The Mirthful Menace and The Jester of Genocide.
 * Joker was so "insane" that Deadman was barely able to possess him for even a few seconds.