u/0hBlasta

It left me shocked, but after rewatching all I can tell is most of what happened have been acts on impulse and his stupid love for Hannah. What it looks like to me is that Dexter thought he finally escaped the dark passenger, but he didn't even realize it totally took over. I feel like this was the best scenario the writers took after being forced to not kill off Dexter.
Though I will agree the death of Debra was genuinely fucking terrible.