tainted

This word carries a heavy sense of permanent damage or corruption. It suggests that a once-pure substance or a clean record has been infiltrated by something foul, making the entire entity unacceptable or unreliable. It is more severe than "dirty" and more specific than "damaged." In social or professional contexts, it describes a loss of integrity that is difficult to reverse. A tainted legacy or a tainted witness implies a fundamental flaw that renders the subject untrustworthy, regardless of any other positive attributes they may possess.