These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
YMMV: The Black Cauldron
Alas, Poor Scrappy: Gurgi sacrifices himself to destroy the Cauldron Born Army, but he is resurrected.
Anticlimax Boss: Despite all the build up the character had, the Horned King doesn't put up much of a fight before he is sucked into the cauldron: He lunges unarmed at Taran and grabs him, showing no display of powers or fighting abilities whatsoever, and is killed when Taran pushes him in the general direction of the cauldron.
Counterpart Comparison: With Link. Predating The Legend of Zelda by a year, Taran wears clothes and carries a sword strikingly similar to those of Link in his very early years. Plus looting dungeons, working well with animals, wielding a magic sword, having to stop a very old Big Bad from getting an artifact of great power, and breaking lots of pots. Also, Eilonwy seems to be this to Zelda.
Peter Jackson and Andy Serkis seem to have taken inspiration from Gurgi's voice and mannerisms...
Ensemble Darkhorse: The Horned King. Even if the movie failed at the box office and is one of the lesser known Disney feature films, The Horned King is a cult favorite within the Disney fandom and many times is compared with the likes of Maleficent and Chernabog. Probably the only reason why this movie is his only appearance within the Disney universe is because he's Nightmare Fuel incarnate and so would traumatize younger viewers in further appearances. Fans have even already demanded Disney to let The Horned King to make a main appearance in future Kingdom Hearts games. Being played by John Hurt probably has quite a bit to do with it. He had a cameo in House of Mouse, for what that's worth.
And Japanese Love the Horned King: Popular enough to appear in several video games as the Final Boss and to be the center of the Cinderella Castle Mystery Tour at Tokyo Disneyland. Heck, if anything, he's a constant throw in for a possible Kingdom Hearts villain for what it's worth.
Nightmare Fuel: The Horned King and the Cauldron Born; indeed, the entire sequence from the latter's creation until their demise. The Horned King is one of the most visually terrifying Disney villains of all time, second only to Chernabog in Fantasia.
In the climax of the castle tour attraction at Tokyo Disneyland, you face the Horned King and get to watch him as he raises the skeletons lying on the battlefield in front of you as Cauldron Born. And it takes place inside a dark cavern. With realistic audio-animatronics. It's as terrifying as it sounds.
Nightmare Retardant: The Horned King's theme music is frightening—until that 80s synthesizer kicks in and makes the sound of a B-movie slide whistle.
Quality by Popular Vote: it could be argued that the film has suffered from this. Because it was unpopular in the theaters, it's been severely underrated. Although there is good reason it was unpopular in theaters. Many, if not all, characters in the movie are considered to be the Scrappies of the Disney Universe, with Gurgi and Creeper being the most universal. It doesn't help that the plotting and pacing of the movie is quite inconsistent and it seems to lack a proper theme.