Which word best defines a person lacking moral principles?

The term that best defines a person lacking moral principles is "unscrupulous." This word specifically refers to someone who acts without a sense of right or wrong and is willing to engage in dishonest or unethical behavior to achieve their goals. The essence of being unscrupulous lies in the blatant disregard for moral standards and the willingness to exploit others for personal gain.

In contrast, "degenerate" can describe someone who has declined from a previously respectable state, which might imply a loss of morals but is more often used in a broader context of character decline rather than a direct commentary on moral principles.

The term "credulous" refers to someone who is easily deceived or gullible, indicating a lack of judgment rather than a deficiency in moral principles.

"Induce" is a verb that means to bring about or give rise to something, and does not relate to the concept of morality or principles in any significant way.

Thus, "unscrupulous" accurately captures the idea of a person whose actions are devoid of ethical considerations, making it the best choice in defining someone lacking moral principles.