If somebody has really done me wrong, I don't feel the anger subside entirely until I get the chance to tell them (face to face preferably) I didn't appreciate what they did, along with anything else I think they really need to be told. It doesn't matter how they take it, how they respond, or what they do with what I say. All that matters, for me to feel vindicated, is that I let the person knows full well what they did is not something I tolerate. Saying it calmly, even coldly, always gets the best results.
I've sent e-mails and even letters to people who have ripped me off. Sometimes they respond and want to fix the problem, depending at what level of management the ripoff happened. But that's a bonus, not the objective. Most don't respond. I never threaten, and keep it pretty short -- after all, it's often partially my own fault if I get ripped off. But that doesn't make what they did any better, and letting them know that is a crucial part, I find, to letting something like this slide into history.
I'd only sue someone if what they did to me caused me or someone in my family tangible losses, for which I had to pay dearly, AND I knew that litigation was the only way to get a proper redress from them. I don't believe emotional suffering can be quantified with money, or that money can ease emotional suffering.
Someone would have to physically threaten me or someone I love before I assaulted them in anger. In any other case, I've got too much to lose.
When I'm really frustrated or pissed off, I find a place where I can yell at the top of my lungs for a minute or two. Works wonders. Works as well as hitting things, without nearly the physical risk (unless your vocal cords are already on shaky ground, or what you use to make your living).