unfasten vs undo

unfasten and undo both are verbs.

Word	Noun	Adjective	Verb	Adverb
unfasten	No	No	Yes	No
undo	No	No	Yes	No

As verbs, undo is a hypernym of unfasten; that is, undo is a word with a broader meaning than unfasten:

unfasten (verb)	undo (verb)
become undone or untied	cancel, annul, or reverse an action or its effect
cause to become undone	cause to become loose
	remove the outer cover or wrapping of
	deprive of certain characteristics
	cause the ruin or downfall of