A lawful evil villain methodically takes what he wants within the limits of his code of conduct without regard for whom it hurts. He cares about tradition, loyalty, and order but not about freedom, dignity, or life. He plays by the rules but without mercy or compassion. He is comfortable in a hierarchy and would like to rule, but is willing to serve. He condemns others not according to their actions but according to race, religion, homeland, or social rank. He is loath to break laws or promises. This reluctance comes partly from his nature and partly because he depends on order to protect himself from those who oppose him on moral grounds. Because they may be forced to honor an unfavorable contract or oath they have made, lawful evil characters are usually very careful about giving their word. Once given, they break their word only if they can find a way to do it legally, within the laws of the society.
These characters believe in using society and its laws to benefit themselves. Structure and organization elevate those who deserve to rule as well as provide a clearly defined hierarchy between master(s) and servant(s). To this end, lawful evil characters support laws and societies that protect their own concerns. If someone is hurt or suffers because of a law that benefits lawful evil characters, too bad. Lawful evil characters obey laws out of fear of punishment.
Some lawful evil villains have particular taboos, such as not killing in cold blood (but having underlings do it) or not letting children come to harm (if it can be helped). They imagine that these compunctions put them above unprincipled villains. Others may commit themselves to evil with a zeal like that of a crusader committed to good. Beyond being willing to hurt others for their own ends, they take pleasure in spreading evil as an end unto itself. They may also see doing evil as part of a duty to an evil deity or master.
Lawful evil is the alignment which represents methodical, intentional, and frequently successfully evil (in stark contrast to the unstable and self-destructive chaotic evil alignment). It is sometimes called "diabolical," because devils are the epitome of lawful evil. An iron-fisted tyrant and a devious, greedy merchant are examples of lawful evil beings.
The infernal Nine Hells of Baator embodies this concept.