Difference between Never-say-die and Unsubduable

What is the difference between Never-say-die and Unsubduable?

Never-say-die as an adjective is that doesn't give up in despair; indomitable while Unsubduable as an adjective is that cannot be subdued; indomitable.

We hope you now know whether to use Never-say-die or Unsubduable in your sentence.