政府医生 over dosage patient or gave instruction to patient to take drug wrongly，Can I say the doctor is the Drug Kingpin?

No!

A kingpin is a person that control/monopolize a business or owned majority of the resources of a product/service. First, a drug kingpin is usually being referred to illegal drugs trades; second, a doctor/hospital does not own/manufacture the drugs or trade the drugs, they buy/distribute the drugs to patients based on the illness. Sometime this row is called to administer drugs.

You may call the doctor wrongfully administered drugs or is malpractice.