<human>: In 2007, my father left my mother to have an affair with another woman, they had been married 15 years but argued regularly and it wasn't particularly a surprise when he left, apart from to 10 year old me. 

For the first two weeks my father remained very much in my life, he visited most days and spoiled me as much as he could. However, as time went on he visited less frequently until a few months after the initial split, when he didn't visit again. This caused me to develop a lot of issues, especially with controlling my anger and due to this I still harbour quite a lot of resentment for my father.

After 5 years, now 2012, when I was 15, I made a false facebook account (I know it was shifty) and tried to add my father on facebook so I could find out more about his new life. All I found then was an 'up to date' photo, of him and his 'mistress' [35ishF]. 

Skip forward to yesterday and I accidentally logged into the false facebook account I created 3 years ago. Apparently, my father had accepted my friend request even though the account was clearly fake and literally created by a child, hence why I expected the idea to never work and promptly forgot about it.

After looking around his account I discovered he married the woman he left my mother for and has had a child with her, a boy who is now 1 year old... The worst thing about finding this out is seeing the love he gives to this child, after ditching me aged 10, and the amazing person his new friends and family see him as.

So, Reddit, what do I do? Do I act vengefully and try and show everyone who he truly is, as retribution for the damage he did to me? Or, do I use this opportunity to give forgiveness and try to reconcile years of pain and regret?

Can you summarize the given text in a few sentences?
<bot>: My father accepted my friend request on facebook, after walking out on my mother and I 8 years ago, to pursue a new life with his mistress. What should I do reddit?