In Ouat true love’s kiss has broken many curses. The curse with Emma and Henry then later with Regina and Henry. Snow and Charming, true love kissed. Belle and Rumpel almost true love kissed, but Rumpel didn’t want it, so it stopped working halfway.
Sure, and that would give strength to the legend of True Love’s Kiss, like all of the craziness attributed to the full moon in the real world. No reason TLK has to really be that way in-universe, or that it has to be that way completely. Maybe it only works on certain kinds of curses. Maybe the Dark One isn’t even a curse; after all, it started as a backfired perversion of a blessing, not as a plan to deliberately hurt people.
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