No.
My ex did cause my permanent brain injuries and others have hurt me in unbelievable ways, but, I am not perfect, I have hurt people too (although not to the extent I was damaged).
I feel as though if I were to write a letter like that, it would make me just like him, ie, leaving a legacy of pain in my wake.
I am not sure that he actually feels pain. I suspect he is a sociopath; however, that is not who I am or who I ever want to be. And ultimately, this is my choice, no one else's - so the only person to blame is me.
I want to move on without regret, anger, hate, etc. I want to go with peace in my heart if I can.