Gotham itself is shown to be a depressingly corrupt Wretched Hive. Prostitutes can solicit a young boyin front of his parents openly. Corrupt cops like Lt. Eckhardt openly operate in the pocket of crime bosses. The public at large celebrate the Joker — a man who just previously had launched a chemical terrorist attack on the city that killed several horrendously — because he drops cash on them.
The chilling moment when Batman first appears onscreen, looming over two petty thugs and opening his massive wings like a ghastly gargoyle, marvellously sets the tone of his mythical character. The fleeing villains were paralyzed with terror as the monstrous living-shadow stood up unharmed from their barrage of gunfire, and were driven so mad with fear that they can only incoherently cry to the police:
Batman's awkward "smile" that he gives Jack Napier in the Axis chemical plant can come off both as Narmy and this. Especially, for Jack's brief perspective when Batman does his legendary Stealth Hi/Bye to him.
[Jack staring at a smiling Batman]
Jack: Nice outfit. [turns, bends down and grabs gun and takes aim only to see that no one is there]
Batman's walk through Axis Chemicals, quietly and brutally disposing of mooks could qualify too - especially the instance in which he uses his grapple-gun to dangle a mook by his shoulder over an open fall and leave him wailing to be let down. Even Commissioner Gordon and his squad seem taken aback;
And the buildup to the reveal of his face when he corners Grissom, with his face veiled in shadows. You can just make out his bleached white skin as he moves closer and closer into the light then steps out, revealing that green hair and legendary Slasher Smile.
The Lethal Joy Buzzerscene. Before, during and especially after. After the Joker offers to shake hands with a naysaying Antoine Rotelli, his Joy Buzzer electrocutes the subordinate so severely that his entire body is burnt to a crisp; not helped at all by Jack taunting said corpse and breaking its neck with Rotelli's own necktie.
Joker: You are a vicious bastard, Rotelli. And I'm glad you're dead!
The Smylex commercials, and the female newscaster who died with the Joker's smile on her face. And the fact that this was the short version.
There’s also the fact that Joker takes the faces of two models who died in his attack and uses the images of their grinning corpses as co-stars in his commercial (“Love that Joker!”) in a way that would surely haunt any family or fans the models would have had.
Joker's final words for the home viewers watching his "commercial" for his Smylex-poisoned everyday grooming and hygiene products.
The scenes with Joker wearing skin-colored make up in place over his now bleach white skin. It looks just a bit too plasticky to be natural... not to mention, he still has that trademark rictus grin, which arguably looks even creepier on someone who resembles a normal human.
Also, the scene where Joker challenges Batman to reveal himself after the Joker himself "took off his make up". Bruce then pauses the video on Joker's sinister grin and then we are treated to a flashback where it is revealed that The Joker as a young Jack Napier killed his parents. The scene flashes back to Bruce who then turns to the screen in complete shock and the very next scene show is a close up and freeze frame picture of Joker's sinister grin looking straight at the viewer.
That flashback from Bruce's POV feels less like a memory and more like an actual nightmare. The first we see of Jack, he's completely in shadow. Then when Bruce's parents are killed he delivers his pre-mortem line, which sounds deep and has an echo as if he's Death in human form. Finally, Jack steps out of the shadows and he's got that psychotic smile plastered across his face while he takes aim at the 8-year-old Bruce.
Anytime Jack/Joker shows true menace without a hint of irony, such as Jack Nicholson's line reading, "But you can't make an omelette without breaking some eggs", punctuated with breaking Alicia's mask.
Sometime after Jack becomes the Joker, he does..... something to Alicia. Her confident persona vanishes and she begins speaking in a creepy monotone voice all while wearing a white mask. It's only later that Vicky and we the viewers see that Joker has thrown some sort of acid into Alicia's face, scarring her horribly. Vicky is so spooked by the reveal that she immediately starts backing away.
Jack later reveals to Vicki that Alicia was Driven to Suicide and threw herself out a window...or so he says. Either way, he doesn't mourn her death too much, showing just how far gone he truly is.
It is possible Alicia's slowed speech and overall confused, detached state was due to her being heavily drugged, either to keep her under control, or because she was in perpetual agonizing pain from her disfigurement, which most likely was not treated.
In fact, the script explicitly states that she's been drugged during her appearance at the museum scene.
The worst part of it all is, Joker is "smitten" for Vicki, and spends the latter half of the movie stalking and eventually kidnapping her. His treatment of Alicia sets rather firmly in stone what's at stake for her if Batman can't stop Joker from whisking her away.
Imagine being Vicki during the apartment scene. You're just at your apartment, talking to a guy you've been out on a few dates with. All the sudden, the psycho clown creep who harassed you in a previous scene suddenly shows up to...do something to you, after he hints that he might've done something bad to the woman you last saw him with. Your date tries to defend you...only to be told "Ever dance with the devil in the pale moonlight?" as the psycho holds out a snub nosed revolver and shoots your date. Just when he tries to drag you out, he suddenly stops, recites a creepy poem and leaves you behind with a present...which turns out to be a gag involving a hand popping out of the box while holding a bouquet of dead flowers. No wonder she fainted.
When the Joker calmly gives a light-hearted speech to the city that ends on the note "Oh, by the way, I've randomly decided that I'm going to kill you all with the grossest-looking gas ever." You see it coming and everything, but the way he played it is creepy beyond reason.
Joker: And now, comes the part... where I relieve you, the little people, of the burden of your failed and useless lives! But, as my plastic surgeon always said: "If you've gotta go, go with a smile"! Hee hee hee hee ha ha HAAA!
When Batman starts beating the tar out of the Joker in their final confrontation. As much as he deserves every second of it, it still gets horrifying:
Batman socking Joker in the mouth, causing him to pull out his chattering set of teeth; which bite off what looked like a small chunk of his inner cheek or maybe even his tongue. A small, but pretty disturbing moment.
The Joker tries gut-punching Batman and winds up breaking his hand. Batman himself doesn't even flinch.
The cold, ominous delivery of the line "I made you? You made me first". Once the Joker hears that, he's so scared he starts blubbering.
That long, drawn-out scene that ends with the Joker falling to his death. As soon as Batman's grappling line ensnares his leg to a nearby gargoyle statue, you know he's screwed, hesure as hell knows he's screwed, and there's nothing he can do about it as soon as the gargoyle breaks off from the cathedral and starts weighing him down. That POV shot of just how farhe has to fall is downright hair-raising, with the soundtrack effectively playing a dirge for The Joker as he slowly slips down from one rung of the escape ladder to the next... until he's finally pulled off the last one to his grisly, bone-shattering fate far below.
The shot of Joker's splattered corpse; overhead shot, slowly turning as it zooms in, and a horrifying grin on Joker's still-intact face while an incredibly creepy, synthetic-sounding laughnote Which is soon after revealed to be from a small wrapped box, which Commissioner Gordon pulls out of Napier's jacket while investigating the scene. repeats over and over. It's so surreal and unnerving that it really does feel like something pulled straight out of a nightmare.
. Before, during and especially after. After the Joker offers to shake hands with a naysaying Antoine Rotelli, his Joy Buzzer electrocutes the subordinate so severely that his entire body is burnt to a crisp; not helped at all by Jack taunting said corpse and breaking its neck with Rotelli's own necktie.Joker: You are a vicious bastard, Rotelli. And I'm glad you're dead!