vanish vs lessen

vanish and lessen both are verbs.

Word	Noun	Adjective	Verb	Adverb
vanish	No	No	Yes	No
lessen	No	No	Yes	No

As verbs, lessen is a hypernym of vanish; that is, lessen is a word with a broader meaning than vanish:

Other hypernyms of vanish include decrease, diminish, fall.

vanish (verb)	lessen (verb)
get lost, as without warning or explanation	decrease in size, extent, or range
decrease rapidly and disappear	wear off or die down
cease to exist	make become smaller
pass away rapidly
become invisible or unnoticeable