From the very first words on the very first page of your story, you've made a promise to the reader. You've promised them conflict. Surprises. Disasters. Secrets. Change.
And you've promised that, at some point, time will run out and everything delivered through the middle of the story will collide.
Therein lies the climax.
The promises you've made determine how your story can end. If you've built up to a fiery crash and burn, then you'd better deliver or the reader will be left disappointed. If you've built up to a quiet revelation, the character should have that clear "come to Jesus" moment.
There is a plethora of options available--you're not limited in terms of what could potentially happen--but you can't violate the promise.
The ending should satisfy.
Be Brilliant!
~Katie~
