blitz vs onset

blitz and onset both are nouns.

Word	Noun	Adjective	Verb	Adverb
blitz	Yes	No	Yes	No
onset	Yes	No	No	No

As nouns, onset is a hypernym of blitz; that is, onset is a word with a broader meaning than blitz:

blitz: a swift and violent military offensive with intensive aerial bombardment
onset: (military) an offensive against an enemy (using weapons)

Other hypernyms of blitz include attack, onrush, onslaught.

blitz (noun)	onset (noun)
a swift and violent military offensive with intensive aerial bombardment	(military) an offensive against an enemy (using weapons)
(American football) defensive players try to break through the offensive line	the beginning or early stages

blitz (verb)	onset (verb)
attack suddenly and without warning