David and Kathryn
This couple was brought together because of Regina and the effects of the curse. Since we were all rooting for Snow and Charming from the very start in season 1, David and Kathryn together were just wrong. Not only because they were forced together during the curse, but because it was obvious how they didn't fit as a couple. They tried, but it wasn't clicking. And that's because they weren't' meant to be.
Henry and Cinderella
I think most of us hardcore Oncers would agree that Once Upon a Time season 7 was like a fever dream. I try not to think about it too much to be honest. The series tried to make Henry and Cinderella Snowing 2.0, but it didn't work in my opinion. I don't think the actors had great chemistry or a great story together in Hyperion Heights or even the Enchanted Forest. I just was not invested in their story. For some reason, something felt like it was missing and it didn't work.
Belle and Rumple
Ah, Rumple and Belle. This one is a difficult couple. I'm glad that the two end up having a happy ending. Gideon is born, and that episode of Belle dying still gets the waterworks going for me. And especially for Rumbelle fans, it was nice that the two characters end up reuniting in death at the end. They did have their good moments. But I personally didn't support the relationship. Rumple was toxic and constantly lied to Belle. He made some bad decisions, and they affected her. And she'd keep going back to him. The back and forth was too much and went on for too long. This relationship definitely gives me mixed feelings.