Writing the villain's point of view
Writing tip: know your villain's story.
"But... I'm not writing their story, I'm writing the protagonist(s)'s story."
Okay, yes, you are. However, the protagonist is only REACTING to what the villain is doing.
"Uh... what if the villain doesn't come on scene until the finale, how will the protagonist act without knowing what the villain is doin
You got me there. I did this, in fact. In "Down in Blood" I thought the villain was the cousin. But truly, it wasn't at all. The protagonist's villain, was their own PTSD, which is another reason why it was written the way it was written. The lead character knew all along who the scariest person in the room was. It was my own writing naiveté which thought there needed to be a human villain. (And, if you read the book, you'll understand exactly where that part of me tried to take over. I'm sorry.)
[Insert record screech sound here] "You mean to tell me the villain ISN'T always a person?"
Of course. Villains can be people (evil villain, and everyday villain); nature, animals, and/or gods (the immoral entity); and even themselves (the internal struggle). See this post for full examples.
Getting back to the villain's story now.
When you are in the throes of writer's block, write the villain's story in a trashable document. It is NEVER meant to see the light of day. But by writing their story, you'll understand their motives (if human/humanistic), and you'll be better equipped to understand EXACTLY where the villain's actions affect how the protagonist(s) react. Added bonus, you've just put words to paper, breaking the writing block.
"But, what if I don't know the villain's story?"
Interview them. This sounds crazy-pants-crazy, but it works. "How did this all start?" Or, "When [name of protagonist] started doing X, how did that make you feel?" Each question you ask begins to form a more realistic story.