Lily Evans and Severus Snape from 'Harry Potter'
No, Lily and Snape were never officially a couple, but a (one-sided) romance certainly existed, and lots of people think Lily should have ended up with Snape.
Let’s say Lily was (somehow) able to forgive Snape for calling her a Mudblood. They reunite, they date, they eventually get married. The problem here is that Snape’s greatest character flaw is also one of the top reasons relationships fail: he’s inherently selfish.
Remember that time Snape told Dumbledore to keep Lily safe, even if that meant letting James and Harry die, and Dumbledore was like “Dude, that’s all KINDS of screwed up”? If Lily had wound up with Snape, that conversation would never have happened, but it still betrays a personality trait that would’ve presented itself later on in their relationship anyway. He’d still be the same person with the same priorities and the same set of values, and if we’ve learned anything about Lily, it’s that she never would have stood for that nonsense. It’s part of the reason she rejected him in the first place: he was sorry he called her a Mudblood but failed to see the problem with calling other people Mudbloods, or allying himself with people who did. He was willing to overlook her blood status because he loved her, not because he believed prejudice was wrong, which was, you know, kind of a sticking point.
Whatever their choices, the end result would have been the same. Just as there’s no version of Snape that would not have been self-serving, there’s no version of Lily that would have married someone so morally misguided. The relationship, then, was pretty much doomed before it began.