breakup vs ending

breakup and ending both are nouns.

Word	Noun	Adjective	Verb	Adverb
breakup	Yes	No	No	No
ending	Yes	No	No	No

As nouns, ending is a hypernym of breakup; that is, ending is a word with a broader meaning than breakup:

breakup: the termination or disintegration of a relationship (between persons or nations)
ending: the act of ending something

Other hypernyms of breakup include conclusion, termination.

breakup (noun)	ending (noun)
the termination or disintegration of a relationship (between persons or nations)	the act of ending something
coming apart	the end of a word (a suffix or inflectional ending or final morpheme)
	the last section of a communication
	event whose occurrence ends something
	the point in time at which something ends