形容詞 thankless:

1. not feeling or showing gratitude- Shakespeare
   同義詞：ungrateful, unthankful
2. not likely to be rewarded
   同義詞：unappreciated, ungratifying

1. I did much for him but what I got was only his thankless complaints.
   我為他做了那么多，但得到的只是他不知感恩的抱怨。
2. She played a thankless role.
   她扮演了一個受累不討好的角色。