I don’t really truly hate anyone, it’s too strong of a word.  But

Dear person I strongly dislike,

You really messed up my life.  :/  I was perfectly happy and you had to throw things off balance and make me unsatisfied with how things were and with myself.  You turned me into someone I regret being, and even though it shaped who I am now, I wish I could just delete that whole chapter of my life, or at least of my memories.  Whatever though.  It’s a waste of time to dwell upon the past.  The past is the past and right now is what counts in my own life so middle finger to you while I go places in life that you never can and never will.

Love,

Me.