Sully (verb)

1. To tarnish or damage the purity or integrity of something; to defile or sully.
2. To cast aspersions on someone or something's reputation or integrity.

Origin:

From middle english "sullien" meaning to soil or tarnish.

Examples:

1. The scandal sullied the company's reputation.
2. His actions sullied the good name of the organization.
3. The accusations sullied her reputation.
4. The pollution sullied the once crystal-clear lake.
5. The incident sullied the otherwise spotless record of the team.