Synonyms for Fierce:

adj.

angry (adjective)
raging.
destructive (adjective)
violent.
hard-fought (adjective)
bloody.
heavy (adjective)
Heightened.
severe (adjective)
severe.
untamed (adjective)
wild, untamed.
violent (adjective)
violent, brawling, outrageous, wild, furious, raging, assaultive, intense, fighting, frenzied, broiling, ferocious, vehement, abusive, tumultuous, uproarious, savage.
violent, menacing (adjective)
bold, strong, intense, passionate, vehement, raving, threatening, wild, murderous, malign, raging, animal, truculent, furious, malevolent, ferocious, frightening, cutthroat, awful, bloodthirsty, howling, untamed, savage, terrible, powerful, venomous, dangerous, stormy, boisterous, primitive.

n.

wrathful, raving, basic, hard-boiled, dangerous, deep-seated, fanatical, awful, gentle, frantic, ruthless, bold, primitive, terrible, animal, blind, sense, desperate, truculent, insane, hard, passionate, bloody, menacing, malevolent, rabid, virulent, bestial, sanguinary, casual, frightening, affective, depth, burning, tough, malign, bitter, aggressive, acutely, grim, untamed, bloodthirsty, murderous, mad, monstrous, irate, venomous, tame, hostile, fearsome. unbridled, frightful, incensed, severe, fearful, thunderous, incandescent, uncontrolled, devastating, turbulent, moderate, threatening, steamed, unrestrained, lowering, apoplectic, inclement, mild, howling, hellish, steaming, destructive, seething. inhuman, heavily, lightly, kind, full on the mouth/chin etc., mightily, hefty, fiercely, powerful, wolfish. humid, raw, muggy, sultry, help, unseasonable. heavy, strong, high. big. concentrated, Heightened, intensive. fierce (noun)
merciless, ferocious, savage, cutthroat, furious, intense, vehement, boisterous, unmerciful, tearing, trigger-happy, bowelless, rough, stormy, violent.
intense (noun)
fervent, ardent, acute, deep.

v.

mean (verb)
inhuman.

Other synonyms:

wolfish, sultry, humid, Heightened, muggy, unseasonable, inclement. bloody, intensive, fiercely, mightily, bestial, threatening. tough, hefty, concentrated, terrible. powerful, desperate. heavily. lightly. heavy. raw. strong. high. fierce
truculent.
murderous
bloodthirsty.
riotous
turbulent.
uncivilized
primitive.
Other relevant words:
hostile, monstrous, bowelless, awful, bloody, raw, truculent, passionate, fervent, tearing, virulent, animal, aggressive, tough, untamed, destructive, raving, wolfish, severe, inclement, heavily, hefty, hellish, unseasonable, rough, intensive, stormy, deep, lowering, malevolent, turbulent, dangerous, frightful, bold, inhuman, cutthroat, heavy, menacing, grim, ardent, murderous, rabid, sultry, concentrated, burning, insane, unmerciful, frantic, powerful, fiercely, sanguinary, primitive, thunderous, bestial, threatening, frightening, bloodthirsty, uncontrolled, strong, Heightened, ruthless, unrestrained, fearful, terrible, merciless, humid, bitter, howling, acutely, hard, mad, wrathful, acute, boisterous, venomous, trigger-happy, lightly, high, desperate, malign, mightily.

Usage examples for fierce

  1. We had a fierce battle with them every night. – A Soldier in the Philippines by Needom N. Freeman
  2. This may be known to the man in black, which makes him so fierce to obtain the ring. – Frank Merriwell's Chums by Burt L. Standish