The Collaborative International Dictionary of English v.0.48:

Forceful \Force"ful\, a.
   Full of or processing force; exerting force; mighty. --
   Force"ful*ly, adv.
   [1913 Webster]

         Against the steed he threw
         His forceful spear.                      --Dryden.
   [1913 Webster]

WordNet (r) 3.0 (2006):

forcefully
    adv 1: with full force; "we are seeing this film too late to
           feel its original impact forcefully"

Moby Thesaurus II by Grady Ward, 1.0:

67 Moby Thesaurus words for "forcefully":
   actively, animatedly, ardently, briskly, cogently, con brio,
   deafeningly, dynamically, effectively, effectually, eloquently,
   energetically, expressively, fervently, firmly, fluently, forcibly,
   glibly, glowingly, graphically, hardly, heartily, imperviously,
   impregnably, impressively, in glowing terms, intensely, invincibly,
   invulnerably, irresistibly, keenly, loudly, lustily, meaningfully,
   might and main, mightily, passionately, potently, powerfully,
   productively, pungently, resistantly, robustly, ruggedly, smoothly,
   soundly, spiritedly, stalwartly, staunchly, stoutly, strenuously,
   strikingly, strongly, sturdily, tellingly, to good account,
   to good purpose, unyieldingly, vehemently, vigorously, vivaciously,
   vividly, warmly, with a vengeance, with pep, with telling effect,
   zestfully