Rise of the Brave Tangled Dragons AU in which Pitch enjoys haunting Rapunzel because she has so many fears. However, each year her dream of seeing the floating lights gets stronger and stronger, so Pitch finally leads Rapunzel out of her tower in hopes of turning that dream into a nightmare.
Of course, Rapunzel turns out to be a lot tougher than either of them initially thought. Pitch is equal parts amused and impressed by her courage, and voila, they part as unlikely friends.
Or they fall in love and share a romantic song, you know, whichever you prefer.