The best revenge is to live a better life than they, and never look back.
I just find it interesting that, despite thousands of years of examples and stories that demonstrate, consistently and relentlessly, that revenge ALWAYS ALWAYS ALWAYS costs us far more than it ever achieves, people STILL want to walk down that bitter road.
Expose what they want hidden.
Beat them to the punch. Put yours in a good light and theirs in a bad one. Otherwise, you are already compromised and will have to hit the ignore button.
Make them believe that their most precious thing whatever that might be has been destroyed...or key their car
Male or female friends?
Anonymously expose their secrets
just make some real friends