The second step is following the guidelines in one of my more famous works (pick anime and gender). But by the time you’re working on attitude, beliefs and morals (or more accurately, lack there be of), you should already have determined their motivation. No matter how evil a villain is, he/she has a motivation behind every action, even if the action is something as subtle as looking at someone in a certain way, and the motivation is as insignificant as satisfying a whim.
Motivation can be a lot of things, and is usually connected to the archetype and any sort of back story the villain has. For example, this guy wants revenge on the hero, but WHY? Somebody hired this mercenary, but WHO? Unless you intend the motivation to be kept secret, it should, for the most part, be partially obvious.
Let’s take another look Jūō. We know the he may kill, steal and swindle to obtain more summons, but why is he so obsessed with summons? Was he surrounded by animals in his childhood? Raised by them? Nobody knows, and I don’t particularly care. He’s a relatively unimportant fellow, and the sort of villain who seems cooler when you don’t know that much about him, like Boba Fett. That’s why I’m not going to give him any sort of headband. This makes him an unknown figure associated with no particular geographic region, raised by either rogue nin or ordinary people. Or animals. But anyways, let’s focus on the here and now. We know he collects summons for their exotic allure and their fighting capability. Therefore, he is motivated by vanity and lust for power. He does, however, show some genuine emotions towards his animals, so we can assume that at least some of his summons are for companionship.
Let’s focus on personality-type things now. Remember, someone who was evil from the very start would be very different from something good/neutral that was corrupted. While the differences are not always predictable, they are noticeable. Also, personality is integral to archetype, so really, you’re just defining specific details on an already roughly defined personality.
Let’s observe our beastly buddy. Jūō, as previously stated, shows genuine emotion to some of his summons. However, some are treated better than others. In a nutshell, the more uncooperative and disobedient and animal is, the less kind he is to it. Also, some animals are treated better because they are more aesthetically pleasing, easier to care for and better smelling. Usefulness, particularly at the present time, will change the treatment of any animal. We can base his personality on 3 comparable stereotypical figures: Circus Ring Master (since he goes through the trouble of training all his various beasts, although only some get star treatment), Army Sergeant (he is usually mean and demanding discipline, particularly if you are troublesome, but he does care for his soldiers, and “must be cruel to be kind”) and Bandit Ring Leader (since he uses his animals to perform various crimes). We can say that while in combat, he is harsh and commanding, in his spare time he likely to loosen up and be nicer to his summons. As for people, it would be safe to guess that he treats them like his less-than-favorite pets, or as tools to be used in his quest for more summons. Living around animals would not be good for one’s manners, so it can be assumed that his crude in most of his formalities. He wouldn’t be a jackass, though; in the animal kingdom, jackasses get thrown to the wolves at a young age.
But enough about my guy, what do you want in a villain? A murderous psychopath who holds only one woman dear to him? A backstabbing prince determined to overthrow his father? A femi-nazi Amazonian determined to free women from ‘male suppression’? A heartless overlord who enslaves any race not like his? A detached warlord fond of systematically slaughtering his foes? A war hammer swinging, fur clad barbarian from the north who wants nothing more than a pint of mead, a plate of meat, a serving wench…and to bash in the face of anyone who denies him? A dark, deathly assassin, driven by revenge to kill those who made his childhood a living hell?