self-will vs willpower

self-will and willpower both are nouns.

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

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

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

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

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