Whiner (noun)

A person who complains or grumbles constantly and excessively.

Origin:

Whine + -er.

Examples:

1. He is a whiner, always complaining about something.
2. She is a whiner, nothing ever makes her happy.
3. The whiner in the back of the class was driving the teacher crazy.
4. He was a constant whiner and no one wanted to work with him.
5. The whiner's complaints were always ignored.