a stain on one's reputation的用法和样例：
- A stain on one's character or reputation; a disgrace.
- He left the court without a stain on his character.
- There is still a stain on the shirt.
- At the moment, Darfur is a stain on mankind.
- Take a close look and you can see a stain on the stamp.
- I noticed a stain on my shirt after I had already left home.