Protagonist
Part of speech: noun
Definition: The main character in a literary work or drama. A leading person in a contest; a principal performer. An advocate or champion of a cause or course of action.
Example sentence: To become a villain, you had to have become disillusioned, and in order to become disillusioned you had to have been passionate about something you believed in that was shaken and ripped from your grasp as a protagonist in that stage of your life, leaving you disillusioned with God, if you will.
Agonist
Part of speech: noun
Definition: Someone involved in a contest or battle (as in an agon).A muscle that contracts while another relaxes.A molecule that can combine with a receptor on a cell to produce a physiological reaction.