war crime vs law-breaking

war crime and law-breaking both are nouns.

Word	Noun	Adjective	Verb	Adverb
war crime	Yes	No	No	No
law-breaking	Yes	No	No	No

As nouns, law-breaking is a hypernym of war crime; that is, law-breaking is a word with a broader meaning than war crime:

war crime: a crime committed in wartime; violation of rules of war
law-breaking: (criminal law) an act punishable by law; usually considered an evil act

Other hypernyms of war crime include crime, criminal offence, criminal offense.

war crime (noun)	law-breaking (noun)
a crime committed in wartime; violation of rules of war	(criminal law) an act punishable by law; usually considered an evil act