Meh, in all honesty there are very fews ways to get revenge without breaking the law. Your sat there thinking "But Atomicide I want revenge, and revenge with meaning, how can I do this without breaking the laws."
All answer presented so far face the issue that there are physical actions involved, therefore, I recommend psychological revenge. Try the following:
1. Call her and say you want to get back together, arrange a time and place, then fail to show up.
2. "accidentally" send a text to her which is meant for some ***** you met that will engage in sexual activities she wouldn't go into great detail about how awesome the sex was etc.
3. Call her cousin who smashed your car and proposition him, explaining you bat for the other team, and only went out with your ex cos she looked like a man, and you wanted to try and fix yourself
4. Send a text t her phone meant for "her cousin" thanking him giving you the evidence she smashed the car, and explain you won't press charged on him.
Then try some of your own. This kind of abuse has no limitations, unless the victim kills themselves, so if you can't live with that, don't try this.