Blackguards can be defined as dishonest or dishonorable individuals who engage in unethical activities. There are several synonyms that can be used to describe such people, including rascals, scoundrels, rogues, villains, knaves, deceivers, imposters, charlatans, ruffians, and miscreants. These words highlight the negative traits of such individuals and are commonly used in literature and media to describe villains or antagonists. By using these synonyms, writers can create vivid and engaging characters that readers can empathize with or root against. It's important to note that while these words can be used to describe fictional characters, they should not be used to judge or label real people without evidence.