tail end vs ending

tail end and ending both are nouns.

Word	Noun	Adjective	Verb	Adverb
tail end	Yes	No	No	No
ending	Yes	No	No	No

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

Other hypernyms of tail end include end.

tail end (noun)	ending (noun)
the fleshy part of the human body that you sit on	the act of ending something
any projection that resembles the tail of an animal	the end of a word (a suffix or inflectional ending or final morpheme)
the time of the last part of something	the last section of a communication
	event whose occurrence ends something
	the point in time at which something ends