I had two villians with close ties, and they both died in the last chapter. Both deaths were "off camera", and both were unexplained, though with inference as to what caused them. I questioned the similarity.
My first thought tempted me to change the second death, or possibly let the man live on to cause trouble in a potential sequel. When I pulled up the chapter and pondered "What do I really want to do?", I decided to change neither death. I did add material around the circumstances to provide a larger perceived difference between the two deaths. The first had been left open as a murder/suicide which could have been staged. I wrote in a broad hint that the other villain staged it, through an organization.
I also left the second death "as is", but added some activity to that villain's last days. I also needed the activity I added to complete a promise made a chapter earlier. I had proposed the villain would be driven to a desperate act, but did not write a desperate act in the last chapter. The book needed that desperate act. I know why it wasn't there. As I wrote the last chapter, I was eager to finish, then go back and read the book. I rushed it.
I also added a dialogue scene between the hero and an ally to wrap up another plot thread which, while not left completely hanging, needed a stronger note concerning its continuation ... a continuation important to 'next in series' should I ever write it.
I'm satisfied I strengthened the last chapter, which was the goal.