a person who actively disagrees

disagreeing, differing

unorthodox

unorthodox

(of) a person who does not agree with and act like most people

unwilling to behave, believe as most do

a person who changes her or his political or religious beliefs and joins a rival group

rebellious

a sect or sects

narrow-minded, exclusive

not in accordance with what is orthodox, conventional, traditional

abnormal; other than accepted