ultimatum
noun [ C ]
uk/ˌʌltɪˈmeɪtəm/ usa warning, usually the last and most threatening one in a series, in which someone is told that if they take a particular action, something unpleasant will happen to them:
issue/deliver/give an ultimatum The chairman has issued an ultimatum: sort out the problems, or the expansion will not take place.
Should I give him some kind of ultimatum to encourage him to retire?