WordNet sense 1 (with unconditional and enthusiastic devotion):

heart-whole

WordNet sense 2 (not pretended; sincerely felt or expressed):

genuine, unfeigned, true

WordNet sense 3 (without dissimulation; frank):

honest

WordNet sense 4 (earnest):

dear, devout, earnest, heartfelt

WordNet sense 5 (sincerely or intensely felt):

cordial

WordNet sense 6 (undertaken in good faith):

bona fide

WordNet sense 7 (characterized by a firm and humorless belief in the validity of your opinions):

solemn

WordNet sense 8 (concerned with work or important matters rather than play or trivialities):

serious