I was mulling over some things about the Disney Renaissance, and I actually noticed that the adaptations for various fairy tales are actually a bit darker compared to the originals. I mean, obviously, The Hunchback of Notre Dame is a contender for the darkest Disney renaissance movie that was a direct adaptation of a story, but there are others, even films that by themselves are somewhat light-hearted. The Classics often tried to tone down the darkness when making the adaptations to the fairy tales (for example, Snow White was aged up to roughly twice her age of that of the original tale to avoid implications that her stepmom was trying to off a pre-adolescent girl, not to mention she actually meets the prince far earlier than in the original tale, who only met her after she was poisoned, and had far less innocent designs for her originally; Cinderella's dad was killed off before the events of the film because in the original tale, he actually contributed a bit to the abuse Cinderella suffered at the hands of her stepfamily; and in Sleeping Beauty, Aurora stays asleep for a whole century and is raped by an ogre prince, resulting in a pregnancy that was powerful enough to awaken her.).
The Little Mermaid
Granted, it's more of a mild example on this list, especially when Ariel actually survives the movie unlike in the book, not to mention has little to sacrifice even with her being permanently made a human (even with her being human and not a mermaid anymore, the kingdom's near the sea, meaning she and her relatives can still visit, especially when the surface ban's most likely undone now). However, the film actually does feature a lot of dark elements that weren't even in the original tale. In the original tale, for example, there wasn't any indicated conflict between merpeople or humans, and if anything it's implied that several of the merpeople want humans to experience their home being unaware that they can't survive underwater. The sea witch was a more neutral entity, and there's no ban on surfacing obviously (quite the opposite, visiting the surface was actually considered a rite of passage). Heck, Ariel actually had no specified time limit as a human being other than making sure Eric fell in love with her rather than someone else. Probably the only thing that actually qualified as dark was the ending, really, and I really wasn't particularly fond of that ending since it came across more as a selfish brat getting her way in the end despite her actions really hurting people in a far more permanent manner than in the film (her grandma is implied to have died from a broken heart thanks to her running away from home to pursue getting a soul, her sisters are effectively cueballs thanks to sacrificing their hair for a chance to save their sister, and being broken hearted when the learned that their sister chose death. Even her prince, who married Vanessa [who had zero relation to the sea witch at all and was implied to be good], was devastated by her death, viewing her like a sister to him). Quite frankly, had I wrote the ending, I'd make darn sure that she gets a soul, but then God sentences her to Hell for all of eternity thanks to what she did.
In the film, however, a large degree of the conflict came from infighting between Ariel and her dad resulting from their differing philosophies on humans, with Triton largely being a really hateful racist against humans (well, technically speciesist, but still), and even implied harboring genocidal thoughts against humans, or at least didn't care if a human died if Ariel didn't interfere despite flat out admitting he didn't know the human in question. In fact, his racist attitude and rage against humans is even largely the reason Ariel ran away from home, especially after an especially violent temper tantrum from Triton (and quite frankly, I don't blame Ariel for doing that at all.). In addition, the Sea Witch was made a lot more villainous, a Machiavellian schemer and was even implied to absorb souls to grow stronger via deals that she's implied to sabotage. She even gave kids during the 1990s nightmares, and she got an extremely violent death, both in the alternate ending and in the final film. Also, Ariel actually had a time limit in the film to do her duty, and if she failed, she got a fate worse than death. Though ultimately it was still somewhat light enough to be considered similar to one of Disney's classics, due to the ending change as well as Ariel largely still being innocent as well as Ariel not sacrificing much.
Beauty and the Beast
Beauty and the Beast, the Disney film, came across as being quite a bit darker than the original tale it adapted from in several respects, many of which were largely Jeffrey Katzenberg's fault (if he considers the result to be much lighter than the Purdum draft, I really don't want to know what qualifies as dark for him). It was arguably very dark for its time, especially compared to The Little Mermaid, even with the otherwise light-hearted songs and a happy end like in the book.
To put it in perspective, in the original tale, heck, even the Purdum draft even, the prince, while still cursed because he didn't let an enchantress/fairy/whatever inside his castle during a cold winter's night (or had the balls to refuse being raped by the fairy), was actually the only one cursed, as either his staff fled during the curse, or otherwise he never had any staff to begin with (there's also little indication that the surrounding area was cursed either). Instead, he just tended to the castle himself. Oh, and he doesn't have a time limit at all (not an imposed time limit anyways) as to whether he can break the curse, the only stipulation that he get a girl to fall in love with him. Beast's interaction with Maurice was a lot nicer in the original tale compared to the film, considering that he was implied to have willingly let Maurice stay for the night, and only got angry when Maurice nearly tried to steal a rose from his garden. Even then, he allowed Maurice to leave without incident after learning about his daughter, although only under the condition that she take his place. Oh, and his death and later resurrection had nothing to do with a mob of angry villagers or a jealous suitor. Also, the concept of sexism wasn't even a theme of the original tale at all, or even lust (heck, Belle didn't even have a rival suitor in the original tale. The actual villain, or villains, rather, were her older sisters). Probably the only thing that actually might qualify as being dark was Belle's family losing their wealth and being forced to live in a farmhouse as a result. Or the fairy trying to rape the prince in one version of the tale. A lot of these were actually retained in the original draft for the film before Katzenberg demanded a total rewrite.
The film, however, had Beast not only being cursed as a result of not letting the enchantress in, but she also went as far as to curse his staff as well, and his castle. If the stained-glass windows are to be believed, she even cursed the forest into becoming an extremely desolate place as well. Then she forced a time limit onto the Beast with an enchanted rose she tried to give to him earlier as a bribe to let her stay for the night, blooming until his 21st year, with the curse being permanent if the last petal fell before he could fall in love with a woman and have her fall in love in return. Considering the director's commentary indicated the curse was psychological and it being strongly implied that the conditions of the curse extended to the servants and castle as well, perhaps even the forest, that basically means that the Beast would be reduced to the mindset of a literal animal by the end of the curse, and the servants would die by turning into literal objects as well, if he failed. And thanks to the forest being strongly implied to be cursed into being a desolate, dangerous place as well, meaning not even those who actually might have been strongly loyal to Beast beforehand could have been able to even attempt to eliminate the curse, Beast's chances of undoing the curse were practically impossible, so it actually is understandable why he'd be in a huge amount of despair. Heck, what's worse is that the enchantress actually got away with it entirely, and this is despite her actions qualifying as reckless endangerment, harming of several minors (while it may be debatable as to whether Beast was 11 at the time he was cursed, we do know that Chip and his siblings were most certainly at most children at the time of the curse), illegal pollution, and even attempted mass-murder. That's just for the opening, BTW. For the film proper, we've got Beast actually acting like a huge jerk to Maurice, locking him up in a dungeon for trespassing as well as for basically unconsciously staring at him, even when the servants tried to vouch for him, and clearly did not intend for Maurice to be in the castle in the first place. And then when Belle became his prisoner instead via a prisoner exchange, Beast removes Maurice from the premises before she could even say goodbye to her dad. Oh, and the entire first night was a huge mess of arguments, Beast really losing his cool (although not without justification, since Belle did commit breaking and entering into the West Wing despite specifically being told not to enter, and without any justifiable excuse either). When Belle does eventually get free, she actually ends up having to sell out the Beast and possibly his servants in order to save her dad from the crazy farm, thus nearly getting them killed as a result (and Beast actually DID end up killed as well). Oh, and thanks to Katzenberg demanding for a feminist bent to the story, and making sure to hire Linda Woolverton, a feminazi writer to push the message, it also had a lot of sexist themes in the movie, namely the villain being the stereotypical sexist pig that one can expect to find in feminist literature, and at one point, Gaston openly gloated that he was going to lock Maurice up in an asylum in public to cheers from the villagers, or at least strongly implied he was going to do so. Oh, and Belle was actually depicted mostly being as somewhat of a jerk like Woody from the Black Friday reel of Toy Story. Sure, it may not have been Hunchback of Notre Dame kind of dark, or even The Lion King kind of dark, but it was definitely very dark, especially when compared to the Classics and even The Little Mermaid, the immediate prior film.
Hunchback of Notre Dame
Granted, the original source for the book wasn't exactly child friendly to begin with, being a High School literature piece at the very least. However, Disney's take on the book actually seemed to exceed even the original tale in levels of darkness, despite otherwise having a happy book and swapping sympathetic traits around (ie, Phoebus being made decent while Frollo was made really bad).
Namely, in the original book, there wasn't any hint at attempted genocide on Gypsies, nor was it even suggested that Quasimodo had gypsy heritage. Frollo was actually decent enough to actually take Quasimodo in and had zero role in his mom's disappearance (in fact, in the original tale, Quasimodo's mom actually DID abandon her son).
In the film, there was a whole lot of gypsy persecution as the theme, and there's a LOT of anti-religious messages in the film, far more than even in Victor Hugo's work. And Frollo was made into a genocidal nutjob as well, even being responsible for Quasimodo's mom's death and even nearly killing Quasimodo as well.
There may be a few more films that might qualify, I'm not sure, though (I know Lion King doesn't qualify as while it does take elements from Shakespeare, it's largely an original work rather than a direct adaptation). I do know that the only film that actually came across as lighter and softer than the original tale as far as I know was Hercules.