From Longman Dictionary of Contemporary Englishstain on somebody’s character/name/reputation etcstain on somebody’s character/name/reputation etcFAULT/something WRONGsomething that damages the good opinion that people have about someone → stain
Examples from the Corpus
stain on somebody’s character/name/reputation etc• Whatever the outcome, he not unnaturally regarded his time in gaol as a stigma, as a stain on his character.• Buy him eine kleine Knackwurst and toddle home without a stain on your character.• Robert Lopez is released without a stain on his character.• Duran dominated Leonard physically that night, but five months later the New Orleans farce put a huge stain on his reputation.• The massacre has left an indelible stain on the name of Clan Campbell. 