I hear you, anon. A person who hurts you repeatedly and takes pleasure in it is not a person you want to stay in a relationship with. And although I think the nature of human interactions is that we inevitably cause each other pain at times, I do think that if Juliette survives, Nick might forgive her for the things she did but they could never be the way they were again, even if they actually talked everything out and both admitted the places they were at fault and the places they weren’t.
One could also argue it the other way, though: Juliette would have been better off without Nick. She would have been better off not being with someone who lied to her, repeatedly put her life in danger, dismissed her emotions whenever they weren’t convenient for him, and caused her a lot of physical harm as well as emotional pain for several years.
Their relationship was very cute at times, but at others it was one-sided and extremely unhealthy, since the very first season. Nick’s greatest flaw is his self-absorption and avoidance, while Juliette’s is/was that if she loved someone, she would be too accommodating of their wants and needs, to the point of ignoring her own. It was a toxic combination that would have torn them apart eventually, in my opinion. Her transformation and all that followed just hastened things along.