Who was a bigger dick? SPOILERS
First of all, I don't quite understand his farewell words just before he put both of them to sleep. "We were just too greedy, baby." Greedy for what? For hurting each other, for paying back?
To try to answer the subject myself, I vote for him, because he dumped her in a much harsher way than him being dumped on that sidewalk after having glimpsed a bit of heaven. Cruel, sadistic. Perhaps the worst, she lost a chance of giving a birth. Only then she caught his manners and payed back substantially.
I am calling them a playful name, dicks, since they were isolated and didn't hurt others.