fierceness(n = noun.attribute) ferocity, furiousness, fury, vehemence, violence, wildness - the property of being wild or turbulent; "the storm's violence"
is a kind of intensity, intensiveness
has particulars: savageness, savagery
Derived forms adjective fierce₄, adjective fierce₃, adjective fierce₂, adjective fierce₁

   the quality of being fierce; ferocity; fury; vehemence. [WordNet 1.5]

N  excitability, impetuosity, vehemence, boisterousness, turbulence, impatience, intolerance, nonendurance, irritability, itching, wincing, disquiet, disquietude, restlessness, fidgets, fidgetiness, agitation, trepidation, perturbation, ruffle, hurry, fuss, flurry, fluster, flutter, pother, stew, ferment, whirl, buck fever, hurry-skurry, thrill, state of excitement, fever of excitement, transport, passion, excitement, flush, heat, fever, heat, fire, flame, fume, blood boiling, tumult, effervescence, ebullition, boiling over, whiff, gust, story, tempest, scene, breaking out, burst, fit, paroxysm, explosion, outbreak, outburst, agony, violence, fierceness, rage, fury, furor, furore, desperation, madness, distraction, raving, delirium, phrensy, frenzy, hysterics, intoxication, tearing passion, raging passion, anger, fascination, infatuation, fanaticism, Quixotism, Quixotry, tete montee, excitable, easily excited, in an excitable state, high-strung, irritable, impatient, intolerant, feverish, febrile, hysterical, delirious, mad, moody, maggoty- headed, unquiet, mercurial, electric, galvanic, hasty, hurried, restless, fidgety, fussy, chafing, startlish, mettlesome, high-mettled, skittish, vehement, demonstrative, violent, wild, furious, fierce, fiery, hot-headed, madcap, overzealous, enthusiastic, impassioned, fanatical, rabid, rampant, clamorous, uproarious, turbulent, tempestuous, tumultuary, boisterous, impulsive, impetuous, passionate, uncontrolled, uncontrollable, ungovernable, irrepressible, stanchless, inextinguishable, burning, simmering, volcanic, ready to burst forth, volatile, excited, exciting, Int, pish!, pshaw!, noli me tangere, filled with fury, rapt, inspir'd, maggiore fretta minore atto.