If you’ve ever sought revenge for any wrongdoing against you, how did it work out in the end? ~

No, revenge is not in my heart.  I did get justice once with a person. 

I certainly thought about it.
Mechanic installed a new engine
in my old truck, $3000.00.
It fell apart, he wouldn't be responsible,
had to get another engine.
Oooh i thought about putting nails
under all of his tires and Every time i saw him i would
flip him off.
But i finally bought another truck, let all of my anger subside,
and now when i drive by his place, sometimes i forget to
flip him off.
...soooo, "almost" to your question...haha.
...But as well...yes, i did get justice once with a client.
They refused to pay after the building inspector gave me
more work to do.
I took her to small claims court. I won but she still refused to pay.
I had to get the Sheriffs to go into her bank account
and take the money that was owed to me.

My cousin disliked a fellow college attendee. He went out and bought a locking gas cap and put it on the guy's car. 

I've never sought revenge for any wrongdoing against myself but I have sought revenge for wrongdoing against others that couldn't defend themselves against such wrongdoing.