I'm going to get cold-hearted revenge on my cheating ex
What makes you want to be cold-hearted towards her?
She cheated on me with two friends in July
It's understandable that you are hurt and want to take justice into your own hands. However, you should start to focus on yourself and your personal goals so that you can move on and move forward from the hurt. You will get justice when your ex sees how well you are doing, and with a new love interest.
I don't want to focus on myself. I want revenge. I want to tear her heart into pieces and shatter it into a billion pieces.
Having so much anger is not good for you and seeking revenge can get you into trouble. It would be better for you to seek help moving on so that you can be happy in the future with someone else.