Book recs that about enemies (who would die for each other) but don’t realize they’re already in too deep – everyone else sees it except them.

Exactly the title. I'm looking for enemies to lovers where they genuinely hate each other first, like real enemies, not mild rivals. They would absolutely try to ruin or even kill each other if needed. But at some point (I want a long slow burn) they'e already in too deep emotionally ad don't even realize [...]