I think really good villains tend to have a traumatic/motivational background that guides their desires but also fundamental personality flaws that lead to them

I think really good villains tend to have a traumatic/motivational background that guides their desires but also fundamental personality flaws that lead to them acting well outside the bounds of normal human behavior. Some modern stories fall down when they decide to just take forever really grinding that explanation into the audience. For example, Ramsay Bolton was a great modern villain. I don't need to spend an hour watching him be sad that his dad was mean to him.