de-escalation vs diminution

de-escalation and diminution both are nouns.

Word	Noun	Adjective	Verb	Adverb
de-escalation	Yes	No	No	No
diminution	Yes	No	No	No

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

Other hypernyms of de-escalation include decrease, reduction, step-down.

de-escalation (noun)	diminution (noun)
(war) a reduction in intensity (of a crisis or a war)	the act of decreasing or reducing something
	the statement of a theme in notes of lesser duration (usually half the length of the original)
	change toward something smaller or lower