Thankless

Adjective

 * 1)  not appreciated or rewarded
 * 2)  ungrateful or unappreciative

Adverbs for Thankless
dismally; sadly;  ungraciously;  grimly; heartbreakingly; utterly; bitterly; tragically; distressingly; drearily; cruelly; amazingly.

Thesaurus
bitter, bootless, careless, despised, disagreeable, dislikable, disliked, displeasing, distasteful, fruitless, futile, heedless, lowly, miserable, misprized, misunderstood, out of favor, profitless, self-centered, sour, thoughtless, ugly, unacknowledged, unalluring, unappealing, unappetizing, unappreciated, unappreciative, unattractive, uncared-for, undelectable, undelicious, undesirable, unengaging, unenjoyable, ungrateful, uninviting, unlamented, unlikable, unmindful, unmissed, unmourned, unpalatable, unpleasant, unpleasing, unpopular, unprofitable, unregretted, unrequited, unrewarding, unsavory, unsung, untasteful, unthankful, unvalued, unwelcome, useless, vain, wretched

Etymology
From.

Antonyms

 * thankful