The word mutiny refers to an open rebellion against the officers of a ship or army. A person who takes part in a mutiny is called a mutineer. This matches the question, which describes a soldier or sailor refusing to obey orders.
Compare the other options by context. Radical and revolutionary both relate to political change on a large scale, not specifically to military disobedience. Anarchist relates to opposing all forms of government, which again is not tied to a soldier's specific act of rebellion.
Only mutineer is tied directly to soldiers or sailors defying command, which is exactly what the question describes.
So the correct answer is option C, Mutineer.