Revenge will not bring you peace my friend. What you actually want is freedom from that heavy feeling in your chest, revenge wont make that go away. I know it is very hard. I am in the exact same place as you. First love, 3.5 years and then she leaves in the blink of an eye and is rude to me all the time.
I also feel like wanting revenge. I want to beat the other guy to death at times. Ruin his life, destroy his entire family. But I am not the villian here. I am a good person. I actually care for people. You seek revenge it will just give one more excuse to her to say she was right in leaving you.
Never do a thing which will ever give her a chance to say this. You loved her and love might seem very hard now when you spend your day in misery but take it from me love is the only way out. I have had 10 months of this. And I can tell from hellish experience that only when I think and do stuff out of love that I feel better. Alternative is not to think of her at all, keep your busy. You will be able to do it is some time.
Be the better person, and have some faith that the 3 years you spent will have left its indelible mark. I understand you pain bro, I was also feeling vengeful a just 2 days back. But it is not the right way.
It is hard but swallow it. This experience will make a man of you. Never show anger, keep cool. And many guys and girls go through this same shit, so you are not alone. They survive, you will too.