Psycho surgery : Severing or disabling areas of the brain to treat a personality disorder, behavioral disorder or other mental illness.
Electroconvulsive therapy : It is psychiatric treatment in which seizures are electrically induced in patients to provide relief from mental disorders.
Antipsychotic drugs : Drugs used to treat psychosis.
Antianxiety drugs : Any drug that relieves symptoms of anxiety.
Of the given options, Psycho surgery causes most serious form of brain damage.