weaken vs de-energise

weaken and de-energise both are verbs.

Word	Noun	Adjective	Verb	Adverb
weaken	No	No	Yes	No
de-energise	No	No	Yes	No

As verbs, de-energise is a hyponym of weaken; that is, de-energise is a word with a more specific, narrower meaning than weaken:

weaken (verb)	de-energise (verb)
become weaker	deprive of energy
lessen the strength of
reduce the level or intensity or size or scope of
lessen in force or effect
destroy property or hinder normal operations