I believe in Divine Justice! 
As you know, someone recently did something so nasty to me, it took
me by complete shock and for a few days thereafter, I was out of
sorts.
After the initial shock wore off, I quietly contemplated the issue
and somehow, instead of actively plotting revenge, I felt the best
thing to do would be to leave it to God, who definitely saw the
injustice, and in His time, in His way, will set things
right.
I'm kinda too lazy to plot for revenge, and I know too well how
anger and all that can slowly wear your spirit down. 
I'm slowly closing one chapter of my life, and moving on to a new
life. And what I definitely wouldn't want to carry along with me,
are burdensome baggages like bad memories, negative emotions, and
insincere 'friends', etc. What does not make a positive
contribution in my life, gets trashed before I embark on my new
journey. 
So, revenge? Nah... better to react with apathy at worst, kindness
at best.
Better to let God handle all these things
instead of taking things into our own hands!