Saying that The Joker is psychotic is like saying Superman can fly; it isn't really a surprise. His sheer madness is quite endearing to the majority of DC's fanbase, with the character becoming a pop culture icon that seems to have almost eclipsed the hero he has a bitter rivalry with, Batman.
Voiced by Luke Skywalker himself, Mark Hamill, The Joker in Batman: The Animated Series is far more controlled than his comic inspiration, though he isn't usually sympathetic. With that being said, he occasionally can muster some moments that make the audience feel kind of bad for him... emphasis on occasionally.
Felt Bad: Beware The Creeper
Now, Joker is responsible for turning reporter Jack Ryder into the manic Creeper in "Beware The Creeper," but the ordeal that ensues is completely out of his hands. After The Creeper gains his zany outfit, he comes across Harley Quinn, with whom he is instantly smitten.
Terrified by his lunacy, she turns to The Joker, who initially tries to kill in his usual fashion. Alas, The Creeper survives, chasing Joker and Harley and driving The Clown Prince of Crime crazy, which is really saying something.
Hated Him: Christmas With The Joker
"Christmas With The Joker" is a Christmas tradition for many Batman fans despite the fact that it isn't really... good. The Joker's characterization wasn't quite there, and Mark Hamill wasn't yet comfortable in the role, but this episode is a showcase of The Joker's cruelty.
Joker takes Commissioner Gordon, Harvey Bullock, and Summer Gleason hostage, keeping Batman and Robin busy by blowing up a bridge with a train heading rapidly towards it. When Gleason reveals that her mother is on the train, Joker shows nothing but indifference, even claiming that it will make the crash more humorous for him.
Felt Bad: Joker's Wild
An underrated gem of The Animated Series also sees one of Joker's more understandable schemes. When a struggling billionaire uses The Joker's visage as inspiration for a casino, Joker becomes enraged that he used his image without consent, so he makes plans to destroy the facility.
This, naturally, summons The Dark Knight, who soon puts together that the billionaire, bleeding money, is using The Joker's plan to destroy the casino to make out like a bandit in insurance money. Once this plan hits The Joker's ears, he soon becomes more interested in running the place himself, and by any means necessary.
Hated Him: Joker's Favor
Always be careful to watch your temper in traffic, for you could end up with the same fate as poor Charlie Collins. When Collins yells at The Joker on the freeway after a rough day at work, Joker hunts him down and agrees not to murder him if he does him a favor.
Several years later, Joker tracks Collins down in Ohio, threatening his family unless he makes good on their little deal. Naturally, the deal doesn't go to plan, and Collins soon finds that The Joker's favor will prove fatal for him, as well as several other people.
Felt Bad: Make 'Em Laugh
Joker's plan is far less ambitious than his usual fare, as, in this episode, he merely wishes for the title of "The Greatest Comedian in Gotham." However, his methods of obtaining said title are a bit on the barbaric side.
A year prior, The Joker had attempted to force himself into a stand-up competition, yet was thrown out in the middle of his act. Years later, he uses The Mad Hatter's mind control technology to manipulate the judges into committing inane crimes, which is the only thing that goes his way in the episode.
Hated Him: The Laughing Fish
An adaptation of the comic story of the same name by Steve Englehart and Marshall Rogers, "The Laughing Fish" has one of The Joker's most famous schemes, yet also one of his most sadistic. The Joker attempts to market fish that have been poisoned by his Joker Gas.
When the copyright clerk tries to politely turn him down, Joker becomes hostile and threatens to murder him. This episode shows Joker at his most menacing as well as his most dastardly, as The Ace of Knaves ends up making good on his threat.
Felt Bad: Joker's Million
Another adaptation, this episode sees a down-on-his-luck Joker inherit $250 million from King Barlowe, one of his rivals. In a nice change of pace, Joker legitimately reforms, using his money to live lavishly rather than commit mass murder, which really irks Batman.
Just as Joker's life becomes truly comfortable, The IRS muscles in on him. With the threat of Blackgate looming, Joker attempts to round up The IRS' cut, only to find that all the money that is left is counterfeit. King Barlowe sends his regards.
Hated Him: Mask Of The Phantasm
Batman: Mask Of The Phantasm is arguably the greatest Batman movie in history, with Joker being at the very center of its plot. While The Joker plays a pivotal role in the current plot, his role is subtly expanded in the flashbacks. The film gives little glimpses of a pre-chemical bath Joker when he worked for mobster Sal Valestra.
His role is fairly small here until a shock twist towards the end reveals that the mobster who would become The Joker murdered Andrea Beaumont's father, leading to her becoming The Phantasm. If that sounds like a spoiler to you, don't worry, the twist was given away via a toy before the movie came out.
Felt Bad: The Man Who Killed Batman
One of Mark Hamill's favorite moments from Batman: The Animated Series, "The Man Who Killed Batman" sees a scrawny nobody named Sid The Squid seemingly murder The Caped Crusader, sending shockwaves across Gotham. Among those affected is The Joker, who is unable to accept that Batman is no more.
With Sid's reluctant assistance, Joker stages a crime, but, when Batman never arrives, The Joker becomes depressed, as now crime has no punchline. The Joker holds a mock funeral for Batman, delivering a hilarious eulogy before sending the coffin into a vat of acid... with Sid inside.
Hated Him: Mad Love
One of many areas where the film Suicide Squad failed The Joker was how it portrayed his relationship with Harley as a boring, obtuse love story. In reality, their relationship is far more one-sided on Harley's part.
A seemingly fun and lighthearted deep dive into Harley's backstory and relationship with The Clown Prince of Crime turns uncomfortable on a dime as Joker demeans and abuses Harley for attempting to kill Batman. Regardless of his dalliances with sympathy, The Joker is an absolute monster, and "Mad Love" is evidence of that.