Antonyms of adj grateful

2 senses of grateful

Sense 1
grateful (vs. ungrateful), thankful -- (feeling or showing gratitude; "a grateful heart"; "grateful for the tree's shade"; "a thankful smile")

ungrateful (vs. grateful), thankless, unthankful -- (not feeling or showing gratitude; "ungrateful heirs"; "How sharper than a serpent's tooth it is / To have a thankless child!"- Shakespeare)
        => unappreciative -- (not feeling or expressing gratitude; "unappreciative of nature's bounty")

Sense 2
grateful -- (affording comfort or pleasure; "the grateful warmth of the fire")

INDIRECT (VIA pleasant) -> unpleasant -- (disagreeable to the senses, to the mind, or feelings ; "an unpleasant personality"; "unpleasant repercussions"; "unpleasant odors")

Similarity of adj grateful

2 senses of grateful

Sense 1
grateful (vs. ungrateful), thankful -- (feeling or showing gratitude; "a grateful heart"; "grateful for the tree's shade"; "a thankful smile")
       => appreciative -- (feeling or expressive of gratitude; "was appreciative of his efforts"; "an appreciative word")
       => glad -- (feeling happy appreciation; "glad of the fire's warmth")

Sense 2
grateful -- (affording comfort or pleasure; "the grateful warmth of the fire")
       => pleasant (vs. unpleasant) -- (affording pleasure; being in harmony with your taste or likings; "we had a pleasant evening together"; "a pleasant scene"; "pleasant sensations")