For the person who breaks up with someone, you are probably going to hear how your, now ex, hates you. They may lash out and say things to try and hurt you as much as humanly possible. This is because you have just devastated them. You need to keep quiet and take it.
You have just taken someone's life and torn it apart. You cannot expect this person not take this lightly. And be warned, what comes around, goes around. And you may be the one who gets dumped one day.
For whatever reason your relationship has ended, make sure you are as kind and empathetic as possible. These feelings are normal, and justified many times. Partners feel this because, love remembers.