I don't know what you did, but I know you did something.
Now I'm not gonna pretend that I know the full story of what happened between the two of you, but I will tell you what I am seeing.
I see an arrogant, self-rightous, self-absorbed prick who thinks that his pain is a good "reason" to be harmful to others.
I see an asshole who thinks that giving someone fucking Alzheimer's is "justice" despite the fact that really, he's not punishing the person he hates but the people around them.
How you ask-?
By letting them watch helplessly as their friend slowly forgets.
Not just redundant little things such as where he left an object or missing an appointment. But forgetting the names and faces of people he is constantly interacting with, people that care for them as much as he does.
And they can't do anything but watch.
Watch as they are forgotten like a dream, reduced from a friend or even a lover-
Tell me, what do you think of yourself in this regard?
Are you fucking happy? Satisfied?
Did you finally escape what is haunting you?