怨气 (yuàn qì): grievance; resentment; complaint

The boss always favors his relatives, which has built up a lot of resentment among the other employees.

She came home full of resentment, slammed the door heavily, and didn't say a word.

If friends develop grievances, they should talk them out promptly; otherwise, over time, the relationship will suffer.

He has been holding a grudge because he wasn't chosen as captain, and he's not very cooperative during training.

Let out all your grievances; don't keep them bottled up alone. We can figure something out together.