harakiri vs self-annihilation

harakiri and self-annihilation both are nouns.

Word	Noun	Adjective	Verb	Adverb
harakiri	Yes	No	No	No
self-annihilation	Yes	No	No	No

As nouns, self-annihilation is a hypernym of harakiri; that is, self-annihilation is a word with a broader meaning than harakiri:

harakiri: ritual suicide by self-disembowelment on a sword; practiced by samurai in the traditional Japanese society
self-annihilation: the act of killing yourself

Other hypernyms of harakiri include self-destruction, suicide.

harakiri (noun)	self-annihilation (noun)
ritual suicide by self-disembowelment on a sword; practiced by samurai in the traditional Japanese society	the act of killing yourself