Champion (noun)

1. A person who has defeated all opponents in a competition or tournament and is considered the best in their particular field.
2. A person who fights or speaks publicly in support of a cause or idea.

Origin:

Middle english: from old french champion, from late latin campio(n-), from campus "level ground".

Examples:

1. He was the champion of the tournament.
2. She is a champion for equal rights.
3. He is a champion of free speech.
4. She became a champion of the sport.
5. He was a champion for the rights of the underprivileged.