Formal:
* The government imposed a unilateral trade embargo on the country. (meaning the action was taken by one side only, without agreement from the other side)
* The company's unilateral decision to cut wages caused widespread anger among employees. (meaning the decision was made by the company without consulting employees)
* The peace treaty was signed after years of unilateral negotiations. (meaning one side was responsible for the negotiations)
Informal:
* He made a unilateral decision to go to the concert, even though I didn't want to go. (meaning he made the decision on his own without consulting the other person)
* My roommate's unilateral decision to throw out all my clothes was pretty upsetting. (meaning the decision was made without consulting or considering the other person)
* She took a unilateral approach to solving the problem, ignoring everyone else's suggestions. (meaning she acted alone, without considering other perspectives)
Remember: "Unilateral" implies an action taken by one party without the consent or cooperation of the other party.