I think 'Overlord' is a great one. The protagonist, Momonga, is an undead overlord in a new world, and his actions and the way he rules his territory can be seen as villainous in the eyes of some. 'Akame ga Kill!' also has some interesting villain - like characters. The organization in the anime, such as Esdeath, has cruel and power - hungry motives. Another good one is 'Kabaneri of the Iron Fortress'. The Kabane are like villains, and the story also shows how some humans can turn into something close to villains in the face of survival.
I'm pretty sure Valor isn't based on a true story. Usually, if it were, there would be clear indications or it would be widely publicized as such. But in this case, it appears to be purely fictional.
Act of Valor takes inspiration from true events and incorporates elements of real-life military operations. However, some artistic liberties may have been taken for cinematic purposes.
I'm not sure specifically as I haven't read the exact novel. But usually, in such novels, the main villains could be power - hungry individuals. They might be those who have been wronged in the past and now seek revenge in a very extreme way, making them villains in the eyes of others.
Well, in 'villians are destined to die novel', a main theme is probably moral complexity. Villains are not just one - dimensional bad guys. Their actions might be influenced by their past experiences or the circumstances they are in. And then there's the theme of mortality. Their 'destined to die' part shows that no matter how powerful or evil they seem, death is an inescapable end for them. Also, power dynamics could be a theme as they use their villainous powers and face consequences.
I'm not sure exactly as I haven't read the novel. But there's probably a protagonist who is the one becoming part of the villain's family. Then there would be the members of the villain's family, like a powerful and maybe cruel father figure in the family who is the main villain.