crusader
n. countablen. someone who works very hard and with strong feelings to change something in society. You use this to describe a person who fights for a cause they believe is right.
n. a person who campaigns vigorously for political, social, or religious change. Often carries a connotation of moral conviction or intense dedication to a specific cause.
She is a tireless crusader for animal rights.
The local journalist became a crusader for government transparency after discovering evidence of corruption in the mayor's office.
While some viewed him as a visionary crusader for civil liberties, others criticized his methods as being too confrontational for the current political climate.
From crusade + -er.
Often followed by the preposition 'for' to indicate the cause being supported.