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You've chosen a challenging structure. Normally, for a twist ending to land, the reader has to have been given most of the relevant information along the way -- think Sixth Sense. The only succes...
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#3: Attribution notice added
Source: https://writers.stackexchange.com/a/33269 License name: CC BY-SA 3.0 License URL: https://creativecommons.org/licenses/by-sa/3.0/
#2: Initial revision
You've chosen a challenging structure. Normally, for a twist ending to land, the reader has to have been given most of the relevant information along the way -- think _Sixth Sense_. The only successful model for something close to this that I can think of is _Hero_ (2002), which borrows _Rashomon_'s famous trick of telling versions of the same story from different viewpoints. With that in mind, I would suggest going with _more_ not less. Develop your villain's story into its own mini-novel. See all (or many) of the same events again, but from his point of view, knowing what he knows, and then package the two stories together as one book. Of course, that requires him to become the main character of his own story, going through his own journey, and facing his own challenges. It won't be easy to pull off, and might require a lot of new effort, just at the point where you thought you were done, but I could picture the final effect being very compelling.