I was born for this discussion cracks knuckles

First of all, none of these are anything like Watership Down. These are not ultra violent movies but do have a lot of intense moments and darn subject matter

All Dogs Goto Heaven, Care Bears Movie (seriously that book is fcked up), Secret of Nimh, Land Before Time, Rockdoodle, American Tale, Hannah Barabara's Heidi's Song, Hannah Barbara's Rikki Tikki Tavi, Dark Crystal Labyrinth Scooby Doo Zombie's Island Last Unicorn BATMAN Mask of the Phantasm, Flight of the Dragons, The Animated Hobbit, Brave Little Toaster, Coraline, Paranormen, Who Framed Roger Rabbit The Witches

If you want some true spookiness. Find UNICO on Youtube. It is a cute anime movie about a baby unicorn that is hidden by the spirit of the Wind from the gods who wish to destroy it.

At one point, Unico finds a kitty who wants to be human. So unico grants her wish, turning her into a young woman. She gains the attention of a local prince who ends up being a horrid demon.

Unico is forced to battle it and it basically transforms into something that makes the Fantasia beast look like Big Bird.

The movie is not gory or anything but it is probably one of the darker children films I have ever seen. It was fantastic.

https://youtu.be/TlD1cQNFnWs

Scroll through it first to see if it is fitting.