What is a good, secret, way to get revenge on an evil person?

Please no preaching here, I know it would make me sink just as low. Now that we got that out of the way, any ideas? This guy is in ex-boss, and I know for a fact that he is unscrupulous with many people's life savings (financial advisor), I've seen him lie over and over again, then he fired me for not wanting to forge anymore signatures, or let him make inappropriate comments to me. The legal thing is out of the question, because I don't have the money. I know that he is hanging his own noose, but is there anyway that I could quietly hurry that along? Oh, and he is very lawsuit happy too, very intimidating, so nobody in the past as ever come forth about him. No violence please, just witty stuff.