unbend vs straighten out

unbend and straighten out both are verbs.

Word	Noun	Adjective	Verb	Adverb
unbend	No	No	Yes	No
straighten out	No	No	Yes	No

As verbs, straighten out is a hypernym of unbend; that is, straighten out is a word with a broader meaning than unbend:

Other hypernyms of unbend include straighten.

unbend (verb)	straighten out (verb)
release from mental strain, tension, or formality	put (things or places) in order
become less tense, rest, or take one's ease	settle or put right
make less taut	change for the better
free from flexure	make free from confusion or ambiguity; make clear
unfasten, as a sail, from a spar or a stay	make straight
straighten up or out; make straight	extricate from entanglement