* "I'm not afraid of dying. I'm afraid of never having lived." - Dean Winchester (Season 3, Episode 16) While this line isn't explicitly about romantic love, it embodies the core of Dean's character: his desire for connection and purpose, which ultimately manifest in his relationships with his brother Sam and his various love interests.
* "I know you. And you know me. We're not gonna change. We're just gonna keep doing what we do, and we're gonna keep loving each other, even when it hurts. Even when it's hard." - Dean Winchester (Season 11, Episode 18) This quote from Dean's declaration of love to Amara beautifully captures the central theme of their relationship: an intense, passionate love that's both exhilarating and painful, mirroring the challenges they face together.
* "I'm not going to let you walk away from me. I'm not going to let you disappear again. Not this time." - Sam Winchester (Season 11, Episode 18) This line from Sam to his brother, though not about a romantic relationship, embodies the profound love and devotion between the Winchesters. They're willing to sacrifice everything for each other, even if it means defying fate itself.
Ultimately, the quote that best represents the romantic interest of Supernatural depends on your interpretation and what resonates with you. These lines showcase the show's exploration of complex relationships, emphasizing the emotional turmoil and profound commitment inherent in love.