If I may be so bold in recommending my novel, Villain Throne, it ls more modern with guns but combines the slower warfare of trench warfare and huge cities and sieges. There are still powers and martial arts but overall it has a lot of strategy and combat once you get into the story
A villain should be able to persuade you of his goals or reasonings, to have indisputable morality that twists everything you believe and convinces you whole heartedly that he is right and you are wrong. In fact right and wrong, good and evil do not exist and the villain should prove this...