fierce vs tearing

fierce is not a noun while tearing is a noun.

Word	Noun	Adjective	Verb	Adverb
fierce	No	Yes	No	No
tearing	Yes	Yes	No	No

As adjectives, fierce and tearing are synonyms defined as:

fierce and tearing: marked by extreme intensity of emotions or convictions; inclined to react violently; fervid

Other synonyms of fierce include trigger-happy, vehement, violent.

fierce (noun)	tearing (noun)
	shedding tears

fierce (adjective)	tearing (adjective)
marked by extreme intensity of emotions or convictions; inclined to react violently; fervid	marked by extreme intensity of emotions or convictions; inclined to react violently; fervid
ruthless in competition
violently agitated and turbulent
marked by extreme and violent energy