1. Used alone to tell your addressee that what you have just done or what has just happened (usually to your addressee's disadvantage) is fair and just because they did something unfair to you earlier. English = 'Now we're even!', 'Fair's fair!'
2. Used alone to tell your addressee to stop saying or doing something which they think you deserve but which you find either unpleasant or overdone. English = 'Enough is enough!' 'That'll do!' 'Okay, no need to overdo it!'