hara-kiri vs self-annihilation

hara-kiri and self-annihilation both are nouns.

Word	Noun	Adjective	Verb	Adverb
hara-kiri	Yes	No	No	No
self-annihilation	Yes	No	No	No

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

hara-kiri: 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 hara-kiri include self-destruction, suicide.

hara-kiri (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