self-punishment vs penalty

self-punishment and penalty both are nouns.

Word	Noun	Adjective	Verb	Adverb
self-punishment	Yes	No	No	No
penalty	Yes	No	No	No

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

Other hypernyms of self-punishment include penalisation, penalization, punishment.

self-punishment (noun)	penalty (noun)
punishment inflicted on yourself	the act of punishing, or the infliction of a penalty
	the disadvantage or painful consequences of an action or condition
	(games) a handicap or disadvantage that is imposed on a competitor (or a team) for an infraction of the rules of the game
	a payment required for not fulfilling a contract