Nah x Inigo, Brady, or Gerome. Maybe Owain, though I don't think they're all that bad. Male Morgan is, in my opinion, not only her best romantic support, but one of the best supports in the entire game.
Lucina x Gerome or especially Yarne. The former is boring while the latter is cringe-inducing.
I've also heard negative things about Yarne x Female Morgan.
"I bought a ward against [logic] off a traveling fortune-teller. It lets me add two 'n' two and get a pickle."
Just marry anyone with Galeforce together. No matter how messed up it is(Magic x Physical), it'll be worth your while.
Laurent x Noire is one that everyone likes, not because it's romantic but just for hilarity like Henry x Tharja. Nah with most men except Yarne and Morgan are pretty bad since she forces them to marry them. Yarne with most women are also pretty meh, but doesn't really scream OTP, Lucina x Gerome is one of the ultimate hipster pairings. One of the most overrated pairings. Owain's lover supports are pretty lackluster, as in they don't scream "in love" to me. Kjelle is like the closest he's "in love" with to me.
A lot of people bash Inigo in the lovers corner, but he does well with Severa and Kjelle.
Yuri/Shoujo-Ai is the purest love. No questions asked. Oh Poor soul who has lost their love, I will make your heart race once more!