the main character in a story or play

a leading or principal figure in a movement or field

किसी आंदोलन या क्षेत्र में एक प्रमुख व्यक्ति

English Usage: He was a key protagonist in the environmental movement of the 1990s.

Hindi Usage: वह 1990 के दशक के पर्यावरण आंदोलन में एक प्रमुख व्यक्ति था।