willpower vs self-will

willpower and self-will both are nouns.

Word	Noun	Adjective	Verb	Adverb
willpower	Yes	No	No	No
self-will	Yes	No	No	No

As nouns, willpower and self-will are synonyms defined as:

willpower and self-will: the trait of resolutely controlling your own behavior

Other synonyms of willpower include possession, self-command, self-control, self-possession, will power.

willpower (noun)	self-will (noun)
the trait of resolutely controlling your own behavior	resolute adherence to your own ideas or desires
	the trait of resolutely controlling your own behavior