A few words can fit, depending on the tone you want:

  • Nonconformist – classic term for someone who doesn’t go along with prevailing norms.
  • Iconoclast – literally someone who breaks images, but figuratively a person who challenges or rejects cherished beliefs and traditions.
  • Maverick – someone independent-minded, refusing to follow the herd.
  • Heretic – historically used in a religious sense, but sometimes applied more broadly to anyone rejecting dominant beliefs.
  • Contrarian – one who habitually takes an opposing view, though this can imply they like opposing rather than simply thinking differently.
  • Individualist – emphasizes self-reliance and thinking apart from group norms.