Opinionated (adjective)

1. Having or expressing strong convictions or opinions.
2. Stubbornly adhering to one's own ideas or opinions.

Origin:

Late 16th century (in the sense "having or expressing opinions"): from latin opinio(n-) "opinion" + -ated.

Examples:

1. He was an opinionated man who always believed he was right.
2. She was an opinionated journalist who was never afraid to speak her mind.
3. The article was filled with the author's opinionated views on politics.
4. The book was written by an opinionated historian who had a clear bias.
5. His opinionated nature often caused him to be argumentative.