Denigrate (verb)

1. To attack the reputation or integrity of; to speak evil of.
2. To criticize or belittle unfairly; to tarnish or sully.

Origin:

Early 17th century (in the sense "blacken, tarnish"): from latin denigrare, from de- "completely" + nigrare "to make black", from niger "black".

Examples:

1. He was constantly denigrating his coworkers behind their backs.
2. She denigrated the new movie by calling it a piece of trash.
3. The politician's opponents tried to denigrate his reputation by spreading rumors.
4. The newspaper article denigrated the company's business practices.
5. He denigrated the other candidate's qualifications for the job.