I have some general observations about ending a story well. Feel free to skip below my wall of text as usual.
A good ending can be abrupt and mysterious or extremely detailed and far-reached so long as (here is the important part) it matches the rest of the story which proceeded it.
The Ring is an example of a movie which had an abrupt ending that left the story hanging on purpose and had the heroine make a terrible unethical choice which was almost out of character. It matches the horror, trauma, and uncertainty of the rest of the narrative.
The Lord of the Rings is an example of a story which has a fantastic detailed final act. Everything is resolved, even stuff we didn't care about like who ends up marrying Éowyn the shield mainden. The events project forward to let us know how all the surviving characters are doing days and then many years into the future. The entire elf civilization is written off as the elves migrate away from the main continent. This matches the scale and generational themes of the LotR story.
Stephen King swings between both good and bad extremes in this respect. (A few spoilers follow.) Lousy endings are almost one of his hallmarks. The climax of The Stand was just terrible with a dues ex machina climax that was very out of sink the rest of the story. IT was not much better. The protagonists simply beat the monster to death with their fists for crying out loud. I didn't read the Dark Tower series, but my brother did, and he told me this. In the introduction to the final book, King basically announces that his ending will be a disappointment. He goes on to say that storytelling is about the journey, not the destination. He isn't wrong exactly, but that has got to feel awful to the fans who had been following the books right until the end.
Then the guy turns around and writes Jerald's Game which includes the MOST SATISFYING final act of any story I have ever encountered. After the climax which was already nerve-wracking, the plot skips into the future like LotR and details how the heroine goes on to cope with her trauma, grow emotionally, and use what she learned to help others. Reaching forward doesn't seem to fit if you think that the story takes place entirely in the bedroom, but it actually includes a lot of flashback in which half of the plot unfolds. It also delivers the best plot twist in the entire story. It's just fantastic.