Typically, when a comic book series, graphic novel, or book comes to an end, they have a solid conclusion. The characters and their storylines are all tied up in a nice, neat package, and the fans can go on to read something else, but every so often, other endings were written, but never used.
This happens all the time in movies, and thanks to the internet, it's not hard to find alternate endings to films like Scott Pilgrim vs. The World, Blade, Avengers: Age of Ultron, and more. Of course, movies based on comics are one thing, but comic books are something else entirely.
After all, they take a considerable amount of time to create, so when the artist takes their pen to paper, it's usually the final step, and while some pages may be swapped out for others, the ending tends to stand. Still, there are occasions where something changes between concept and creation, which necessitate moving in a different direction.
The comic books with alternate endings or endings that were never illustrated tend to live in a world of rumor before being confirmed, and often, the fans can't help but wonder if a series would have ended better had the creators stuck with their original plan.