The F-B-I- - 1965 The Contaminator 2-11 was released on:

USA: 4 December 1966

The noun form is "contaminant," or "contaminator," depending on the object in question.

The noun forms for the verb to contaminate are contaminator, contaminant, contamination, and the gerund, contaminating.

If you use the word as a verb such as "to doctor an illness" the antonym is "sicken".
If it is used as a noun "The patient was treated by his doctor" the antonym is "Murderer or Killer, or contaminator"

If the plaintiff (government or private individual) is successful in a lawsuit a company can be found responsible for causing the contamination of land. The court can force the contaminator to clean up the contamination and can award damages to the owner of the land that was contaminated. The plaintiff could make transfer of title to the defendant a part of the suit. You should seek the advice of an attorney who specializes in this area of law to discuss your particular case.