n. 25B6; noun
the protagonist in the plot : CHIEF/CENTRAL/PRINCIPAL/MAIN/LEADING CHARACTER, chief etc. participant/figure/player, principal, hero/heroine, leading man/lady, title role, lead.
a protagonist of deregulation : CHAMPION, advocate, upholder, supporter, backer, promoter, proponent, exponent, campaigner, fighter, crusader; apostle, apologist; N. Amer. booster.
opponent.