The movie's intro song "Arabian Nights" originally had much darker lyrics to an already dark song in hindsight to describe the setting of Aladdin. The lines about getting one's ear removed were eventually cut due to being deemed offensive to Arab-Americans and were changed shortly after being released.
"Oh I come from a land, from a faraway place, Where the caravan camels roam, Where they cut off your ear, If they don't like your face, It's barbaric, but hey, it's home!"
The Cave of Wonders. Its entrance is a gigantic tiger head that seems to be alive, with a deep voice.
Gazeem the thief getting eaten alive by the Cave at the beginning. His scream is awful.
The Cave collapses on itself after Abu grabs the Schmuck Bait ruby on the gorilla statue in the Lamp Chamber and presses the guardian's Berserk Button. The entity screams "INFIDELS! You have touched the forbidden treasure! Now you will never again see the light! Of!DAAAYYY!!!" Cue the Lamp pedestal erupting in flames and the water surrounding the pedestal turning into molten lava. The building rage in the cave's voice as it delivers those words makes it all the more terrifying.
As the heroes try to escape from the Cave, we get a shot of what's happening outside; the entrance is writhing and howling in what could be rage, but looks very much more like agony, as everything inside is destroyed.
Abu pulling the sword out of the sword swallower's mouth in "One Jump Ahead".
Genie turned into a rotten zombie form while explaining to Aladdin that his powers forbid him from bringing dead people to life. Bonus points go to Aladdin's reaction to this if you've noticed it—looks like he's about to throw up! Also, he does an impression of Peter Lorre, just to put icing on the cake.
It's implied that he can it's just that he won't since, "It's not a pretty picture. I DON'T LIKE DOING IT!!!"
Aladdin's plan is to claim that he's gonna find another way out, seemingly not convinced that the Genie can get them out of the cave. It may have been a plan to not waste his first wish but Genie reminds him that he really is a being with phenomenal cosmic power.
Aladdin: I don't know, Abu. he probably can't even get us out of this cave. Looks like we're gonna have to find a way outta here. (the Genie immediately stomps his foot in front of him) Genie:Excuse me?! Are you lookin' at me? Did you rub my lamp? Did you wake me up? Did you bring me here, and all of a sudden you're walking out on me?! (stomps the ground as he inches towards Aladdin) I don't think so! Not right now! You're getting your wishes (makes a brief Nightmare Face) so sit down!(Aladdin and Abu immediately sit down on the Magic Carpet)
The deleted ending where the Peddler reveals himself to be the Genie -cut for time, or because people would have left early and missed the gag, but maybe the REAL reason is that it would have ended the movie on an eerie note. This sequence has only been seen by the masses in storyboard form, but the combination of the Peddler/Genie's ominous vocal tone, dramatic music in the background, the sudden unexpected "poof" transformation, and the fast pace of the sequence gives it a strong scare factor. Then, to top it off, the Genie "makes ya look" as in the final ending, except that he does so by letting out a really shrill scream.
Just picture what would happen if it was possible for Jafar to have Genie use his magic to make Jasmine fall in love with him.
Jasmine, still glowing with love after the "Whole New World" sequence, is in her room combing her hair. From behind her appears her father with glazed, red-tinted eyes, speaking in a Creepy Monotone, opening the other door to reveal a leering Jafar, her new husband, standing there. It's like something out of a horror movie.
When Jafar hypnotizes the Sultan, it is usually just long enough to get him to agree with a single decision, after which he is left dazed for a moment before returning to normal. Apparently this has its limits, though, as the Sultan was able to break control when trying to convince him to marry Jasmine to him before. This time, Jafar is asserting direct control, and it's terrifying. Jasmine's growing alarm at her father's state is painfully realistic to boot.
Pretty much the whole scene where Jafar takes over. The palace is absolutely huge, dwarfing the rest of Agrabah. The fact something like that can be picked up like a carrot out of a garden is bad enough, but having it be moved by a friend against his will is still the tip of the iceberg! How Jafar reveals he's the one in charge of the Genie to Al by having him tower over the palace like a mile-tall wingless Chernabog, how minutes ago everything was going so well, Jafar wishing he was the most powerful sorcerer in the world, and Al tries in vain to have Genie miss powering up his target... Someone's having a bad day.
"Finders keepers, Abooboo," indeed.
Jafar's insanelaughter at the end of Prince Ali Reprise and the shot of him slowly looming over Jasmine and the Sultan, who are both defenseless and utterly terrified. The whole scene shifting to a red tint with the music growing very intense as he does it doesn't help in the slightest.
Jafar: Ex-Prince AliiiiiiiEEE HAHAHAHA! AHH HAHAHAHA!!AHHHH HA HA HA!!!
Jasmine nearly suffocating in a giant hourglass and Aladdin's look of horror when he sees the girl he loves about to get buried alive, time literally running out for her. To add to that, the first time she addresses him by his real name was when she was begging him for help.
The Carpet being unravelled and Abu being turned into a wind-up toy. Carpet keeps desperately grabbing for the lamp as he's being unravelled, which adds some extra horror when one remembers he has human-strength sentience.
Genie Jafar. If you didn't already get a Devil vibe from this guy, he transforms from a massive serpent to a gigantic, crimson, fanged, black-taloned, musclebound jinn, perpetually surrounded with plumes of smoke, flashes of lightning, bellowing about how the Universe is now his plaything. Yikes.
At one point when Aladdin is battling Cobra Jafar, he dodges his snapping jaws, jumps on top of his neck, and sticks a sword in there, and Jafar bleeds. Actual. Red. Blood. No wonder the snake screams in pain. He shrugs it off pretty fast afterwards, but still, it goes to show, Aladdin's good, but Good Is Not Soft.
Beheading. It does not happen at any point in the movie but it is mentioned and judging from Jasmine's reaction when Jafar lies that Aladdin has been beheaded and later when Jafar and Iago both imagine what might happen to them when Jasmine is queen it becomes clear that this fate is dreaded on both sides. Considering one of the sequels and the series had near-beheadings, it might just get worse from what the original film had.
It's also crystal clear that Jasmine nearly has her hand cut off for 'stealing' in the market when she's dressed as a commoner.
Aladdin doesn't seem to be bothered by it, but that brief period where it seemed like he was going to be trapped in the cave forever. Imagine if Jafar had actually gotten away with the lamp, and he really did have no hope in escaping. It's like being buried alive, but less claustrophobic.