smirch

a blemish made by dirt; "he had a smudge on his cheek"

an act that brings discredit to the person who does it; "he made a huge blot on his copybook"

smear so as to make dirty or stained

charge falsely or with malicious intent; attack the good name and reputation of someone; "The journalists have defamed me!" "The article in the paper sullied my reputation"