Antonyms of adj half-hearted

1 sense of half-hearted

Sense 1
halfhearted, half-hearted, tepid, lukewarm -- (feeling or showing little interest or enthusiasm; "a halfhearted effort"; "gave only lukewarm support to the candidate")

INDIRECT (VIA unenthusiastic) -> enthusiastic -- (having or showing great excitement and interest; "enthusiastic crowds filled the streets"; "an enthusiastic response"; "was enthusiastic about taking ballet lessons")
                                                                         

Similarity of adj half-hearted

1 sense of half-hearted

Sense 1
halfhearted, half-hearted, tepid, lukewarm -- (feeling or showing little interest or enthusiasm; "a halfhearted effort"; "gave only lukewarm support to the candidate")
       => unenthusiastic (vs. enthusiastic) -- (not enthusiastic; lacking excitement or ardor; "an unenthusiastic performance by the orchestra"; "unenthusiastic applause")