Yes, there's lots of room for creativity and complexity. Often though, when the true antagonist is an internal conflict of some sort -- often a villain or another antagonist that can yell back is helpful.

Sorry for the tardy reply. I would say it's partly a question of genre. If you're writing romance of any sort, readers want the happily ever after ending. They want it to end on a positive ride-off-into-the-sunset happy bow.
Other genres allow for more gritty or ambiguous endings, but you do need to resolve the main story problem or there won't feel like there's any closure for readers.

Can you have more than one antagonist? Sure. Just remember that the more complexity you add, the more plates you have to keep spinning. I don't know how George RR Martin keeps all those plot and sub plot lines going - so many threads to keep tight. Even the BIG antagonist is Game of Thrones has a backstory, an explanation for why he is the way he is. It's always best to have 3 dimensional characters both protagonists and antagonists. IMO

denise

In the back of my mind I've known his story will come to light at some point. My instinct is to let it flow. But I wonder about readers, if they'll come along for the ride. Do I force myself to wrap things up into a pretty bow, or do I allow the story to unfold naturally?

That's a pretty fair read and analogy on Dexter.

Helps to break things down into small pieces sometimes. 😀