Rival : a person or thing competing with another for the same objective or for superiority in the same field of activity. Enthusiast : a person who is very interested in a particular activity or subject. Critic : a person who expresses an unfavourable opinion of something. Indifferent : having no particular interest or sympathy; unconcerned. Aficionado : a person who is very knowledgeable and enthusiastic about an activity, subject, or pastime.