Diehard (adjective)

Stubbornly persistent in adhering to one's opinions, beliefs, or attitudes, especially in the face of opposition or difficulty.

Origin:

First recorded in the 19th century, possibly derived from a reference to soldiers who refused to surrender in battle.

Examples:

1. He was a diehard supporter of the football team and never missed a game.
2. She was a diehard vegetarian and would never eat meat.
3. The diehard fans of the band refused to give up their love for the group even after their popularity declined.
4. The diehard smoker continued to smoke even after being diagnosed with lung cancer.
5. The diehard Republicans remained loyal to their party even in the face of defeat.