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If canon nightmare sans could love, I think he wouldn't hate the person...he would absolutely LOVE there negativity.
But I was thinking if he met someone who was like him but different like a mixture of nightmares personality but kind but not in a annoying way like they can smile (calm and gentle and not energetic and joyful) and nightmare wouldn't be annoyed...maybe there quiet too and not nosy and very intelligent like him than yeah.
If that was the case, he wouldn't hate them....but he may just hate the fact they are making him feel things he believes, he can't feel/ he can't love at all.
But what do you think?