There are many ways to bring about change - two of the biggest categories are physical methods and psychological methods. As you've said, physical methods can include extra-legal coercion or threats of it.
Physical methods can be direct or indirect.
Direct methods range from threats, to bodily forcing the person to perform certain actions, to removing the person from the seat of power. Indirect methods may include boycotts, trade sanctions, or simply acting as if the person weren't there - individual humans really don't have all that much power to do a whole lot, unless other people actually follow their commands or advice. Psychological methods can range from actually convincing the person to change his mind to merely getting him to accept something he doesn't agree with. An example of the latter is when a minority accepts the results of an election that they don't agree with - on the basis of following majority opinion. Another example, is the acceptance of a command from a dictator or upper- management, despite personal objections.