Willing to do wrong things to get what you want, and not troubled about it. A scruple is that small pull inside you that says "I shouldn't" — the hesitation before you lie, cheat or take advantage. Unscrupulous people simply do not feel it, or ignore it. The word is nearly always about money and power. It attaches itself to certain nouns again and again: unscrupulous employers, landlords, dealers, lawyers, developers, businessmen. What they do is exploit somebody weaker — underpay workers, overcharge the elderly, hide what is wrong with what they sell. So it is not the word for a violent criminal; it is the word for someone who stays inside the law, or just at its edge, and takes what they can. It is strong, and it is formal. In court a lawyer says unscrupulous; on the street a friend says "he's a snake." One useful trap to notice: the plain word scrupulous does not mean the opposite in the way you would expect. Scrupulous today mostly means extremely careful and exact — scrupulous attention to detail. So unscrupulous is not simply "careless." Their meanings have grown apart.