Dissenter

Tom was the lone dissenter.

Tom is the lone dissenter.

Freedom is always the freedom of the dissenter.

As my study proceeded, I began to see that an investigation of organizational morality should also explore managerial dissenters, so-called whistleblowers, many of whom take stands against their organizations on grounds that they define as moral.

Near-synonyms: (all sometimes synonymous) Nonconformist, recusant, Free Churchman; autem cackler (archaic cant)

Is it not apparent how vigorouſly they aſſail the whole Body of the Diſſenters, Men of Religious, Serious, Upright and moſt Loyal Principles, under the ſcandalous Names of Fanaticks and Whiggs.