The Oxford Thesaurus An A-Z Dictionary of Synonyms - blacken v.

1) darken, smudge, begrime: The chimney sweep's face was blackened with soot. 2) slander, libel, asperse, cast aspersions on, traduce, smear, sully, soil, besmirch, taint, tarnish, defame, revile, malign, vilify, discredit, denigrate: His article has blackened my reputation.