The word "ungrateful" means "not showing or expressing thanks" or "unkind to someone who has helped them." It is used to describe someone who does not show gratitude or is unkind to those who have helped them.
[ADJ-GRADED 能被表示程度的副词或介词词组修饰的形容词]不感激的;不领情的;忘恩负义的 If you describe someone as ungrateful, you are criticizing them for not showing thanks or for being unkind to someone who has helped them or done them a favour.
[disapproval]
I thought it was rather ungrateful...
我觉得这样做有些忘恩负义。
You ungrateful brat.
你这个没良心的小坏蛋。
Oxford
un·grate·ful/ʌnˈɡreɪtfl; NAmEʌnˈɡreɪtfl/adjectivenot showing or expressing thanks for sth that sb has done for you or given to you 不领情的;忘恩负义的OPP