The strongest narcotic painkiller is fentanyl, which is approximately 70 to 100 times stronger than morphine when given intravenously, states RxList. This medication may be used for the treatment of severe pain associated with cancer, notes the National Institutes of Health's MedlinePlus.
Fentanyl can be prescribed in different forms, including injections, lozenges and transdermal patches. Some narcotic analgesics that are less powerful than fentanyl include hydromorphine and oxymorphine. However, these two medications are still more powerful than morphine, notes RxList. A list of opioid drugs includes codeine, oxycodone, hydrocodone and meperidine, according to WebMD. Codeine is not as potent as the rest of these drugs, and it is usually combined with acetaminophen.