The phrase "byword of reproach" is typically used to refer to a person or concept that is widely known and criticized for alleged faults. Some synonyms for this phrase could be "object of ridicule," "common target of criticism," "butt of jokes," or "stigma in society." Other terms that may convey similar meanings include "pariah," "outcast," "misfit," or "scapegoat." These words carry an implied connotation of social condemnation and ostracism, often due to attitudes or behaviors that go against prevailing norms or values. Overall, the phrase "byword of reproach" and its synonyms highlight the power of social judgment and the potential impact of negative perceptions on an individual or group.