With the discovery of the major tranquilizers called_, it became possible to control psychotic symptoms, including hallucinations, delusions, and aggressiveness.

Neuroleptics or Antipsychotics

Explanation:

Major tranquilizers also known as Antipsychotics or Neuroleptics are a class of drugs primarily used to manage psychosis and psychotic symptoms that includes delusions, hallucinations, disordered thought and aggressiness. Antipsychotics are most effective in relieving symptoms of psychosis in the short term as long-term use of the medication can cause adverse effects like involuntary movement disorder, impotence and weight gain.

An example of an antipsychotic drug is Clozapine.