regret vs compunction

regret and compunction both are nouns.

Word	Noun	Adjective	Verb	Adverb
regret	Yes	No	Yes	No
compunction	Yes	No	No	No

As nouns, compunction is a hyponym of regret; that is, compunction is a word with a more specific, narrower meaning than regret:

Other hyponyms of regret include attrition, contriteness, contrition, remorse, self-reproach.

regret (noun)	compunction (noun)
sadness associated with some wrong done or some disappointment	a feeling of deep regret (usually for some misdeed)

regret (verb)	compunction (verb)
decline formally or politely
express with regret
feel remorse for; feel sorry for; be contrite about
feel sad about the loss or absence of