verb (v)

• grow worse(verb.change)

  Example:
  Conditions in the slum worsened.
  

  Synonym:
  decline, degenerate, deteriorate, devolve, drop
  Antonym:
  ameliorate, better, improve, meliorate
  

  source: wordnet30
• make worse(verb.change)

  Synonym:
  aggravate, exacerbate, exasperate
  Antonym:
  ameliorate, amend, better, improve, meliorate
  

  source: wordnet30
• To make worse; to deteriorate; to impair.(verb)

  source: webster1913
• To grow or become worse.(verb)

  source: webster1913