Personally I think Honey and Joseph Sugarmen take the cake for this one. I mean the poor lady was manipulated into getting a lobotomy for crying out loud (before you tell me about how times were different back then blah blah blah, I’m well aware,this is just what I think).
Close second would be Sarah Lynn and Bojack for obvious reasons.
I get your vision. At least Joseph and Honey sort of had a reason rather then Beatrice and Butterscotch were just unprepared teenagers. I wouldn’t go as far as saying there relationship was “happy” before the death of Cracker Jack. Definitely beyond toxic, but I guess times were different back then. Another good relationship I was thinking of was Joseph and Beatrice. That whole thing with burning all her things traumatized her till she died (literally). Not to mention him threating Beatrice with a lobotomy, “you don’t want to end up like yout mother, now”.