Fervent
Ardent, Passionate, Impassioned
な adjective, noun
ねつれつ
決心 （けっしん） Determination, Resolution, Conviction
熱心 （ねっしん） Enthusiasm, Passion, Zeal
情熱 （じょうねつ） Passion, Enthusiasm
熱烈 （ねつれつ） Fervent, Ardent, Passionate, Impassioned
The "Im" in Impassioned adds intensity. Likewise, the kanji for this word (heat/fever, violent/intense) add intensity.