de-escalation vs step-down

de-escalation and step-down both are nouns.

Word	Noun	Adjective	Verb	Adverb
de-escalation	Yes	No	No	No
step-down	Yes	No	No	No

As nouns, step-down is a hypernym of de-escalation; that is, step-down is a word with a broader meaning than de-escalation:

Other hypernyms of de-escalation include decrease, diminution, reduction.

de-escalation (noun)	step-down (noun)
(war) a reduction in intensity (of a crisis or a war)	the act of decreasing or reducing something