Is cymbalta (duloxetine) considered the most potent antidepressant?

No : however is a class of duel neurotransmitter medications. Which can be stronger than traditional Ssri

None most potent: With many classes of medications, there is no one single "most potent" med. The choice is made after considering the desired effect, likely side effects, possible other benefits, affordability, patient acceptance, etc. Cymbalta (duloxetine) can help with chronic pain, and so is a good choice for people with depression and chronic pain. Failure of this med does not in any way mean older meds won't work.