他痛苦地抱怨着不公平的待遇。

He complained ___bitterly about the unfair treatment.

她非常失望地发现自己考试不及格。

She was ___bitterly disappointed to find out she failed the exam.

她苦涩地抱怨着升职机会总是不公平地给了别人。

She complained ___bitterly that promotion opportunities always went unfairly to others.