adjective. Not feeling or showing gratitude; ungrateful.

adjective. Not likely to be appreciated.

Unthankful; ungrateful; not acknowledging kindness or benefits.

Not deserving thanks, or not likely to be rewarded with thanks: as, a thankless task.

Synonyms See grateful.

adjective. Not acknowledging favors; not expressing thankfulness; unthankful; ungrateful.

adjective. Not obtaining or deserving thanks; unacceptable.

adjective. not appreciated or rewarded

adjective. ungrateful or unappreciative

adjective. not feeling or showing gratitude

adjective. not likely to be rewarded

"That being said, natural charisma goes a long way and even in thankless, underwritten parts, my biggest complaint was that I wanted to see more of the characters."

thankful  

unappreciative  unrewarding  

Herculean  arduous  back-breaking  daunt  fruitless  

bitter  bootless  careless  despised  disagreeable