Creepy OUAT moments :
S1 : Regina lying to Rumple about Belle's death (the scene itself isn't creepy but the way Regina tells about it is very much creepy), The moment you realize Red ate her boyfriend (Peter's blood, flesh and some of his bones can be seen on the snow)
S2 : Wraith scenes, and also the Seer
S3 : Neverland Shadow, Skull Island, Rumpel's resurrection and the Mother Gothel witch (Idk what's that called but the creepy hooded figure that is a manifestation of Rapunzel and David's fear, I still call her Gothel because it is clearly based on Dame Gothel from the original tale)
S4 : Hans' ice statue, Ingrid killing Helga and her body just crumbles off like that, Entire flashback scenes of "Sympathy for the De Vil", The last scene of S4 which is when the Apprentice was possessed by the darkness
Creepy Wonderland moments :
1. All Jabberwocky scenes
2. The Guardian Nyx overall appearance (Imagine if she appeared in front of you inside your house in the middle of the night)
3. Jabberwocky ripping out Lizard's eyes