Not everyone reading this will have seen 'The Black Cauldron.' Disney doesn't really acknowledge the fact that it exists these days, and we think that it's because they know they went too far. Armies of murderous undead skeletons aren't exactly prime Disney fodder.
Even though the Horned King, who is himself a terrifying creation, deserves his fate, we still probably didn't need to see him savagely torn apart by his own evil creations in a vortex of black magic gone wrong.