This is based on opinion. Please don't list it on a work's trope example list.
Nightmare Fuel / The Princess and the Frog
"I promise I'll pay y'all back! I PROMISE!"
During "Friends on the Other Side", Dr. Facilier's face starts flashing in an almost psychedelic fashion beneath a colorful skull (which, incidentally makes him look like one of the aliens from They Live).Or you can watch it here.
Facilier: I HOPE YOU'RE SATISFIED!
What else can you expect from Keith David's booming eerie voice?
"But if you ain't...don't blame me! You can blame my friends on the other side!"
The spirits/ghosts/shadows/whatever Facilier sends to catch Tiana and Naveen were really, really creepy. They move silently and swiftly and you can't prepare with anything. At least one of them appears to disturbingly resemble The Slender Man... which only adds to the Fridge Horror of one of the below examples.
Prince Naveen cringing in pain as Facilier draws his blood into the talisman.
The very creepy sculpture beside Facilier's door.
The sections of damask wallpaper that Facilier's shadow touches morph into a blatant skull-and-crossbone pattern.
Tiana and Naveen's first night at the bayou.
First they encounter a heron who repeatedly stabs its beak at them. They manage to escaping the heron, only to find themselves surrounded by alligators!
The frogs then find themselves on an alligator's tail and the whole horde of gators thrash in the water trying to get the frogs.
Tiana nearly abandoning Naveen to become gator chow out of spite for dragging her into this mess.
Naveen: Psst! Lower the vine! Tiana: Find your own tree! Gators: There he is! Naveen: Help me! Help me get out of the swamp! And once I marry Charlotte, I shall get you your restaurant!
As Tiana pulls Naveen into the hollow tree, the gators taunt them.
Gator 1: You can hop, but ya can't hide! Gator 2: We've got all night!
Whenever the FOTOS' signature chant starts up (bom bom bom bom bom bom bom bom), you know something creepy/terrifying is about to happen.
The council of the FOTOS Facilier meets with to ask for aid in tracking down Naveen. Their expressions of fury and devilish glee are memorable. Keith David's delivery for the scene is pretty disturbing as well. It's almost like he's talking to the audience.
Facilier: Friends, I know I'm in hock to y'all pretty deep already. But seems our little froggy prince lost his way, and I need your generous assistance gettin' him back. (The Voodoo Masks snarl; Facilier laughs) Ha-HA! I hear ya! Now what's in it for y'all? Well... (he takes out a voodoo doll that resembles Mr. LaBouff) ...as soon as I dispose of Big Daddy LaBouff... (conjures a vision of the city) ...and I'm running this town... (snickers evilly) ...I'll have the entire city of New Orleans in the palm of my hand. And you'll have all the wayward souls your dark little hearts desire. (He blows over the envisioned townsfolk, whose souls fly into the nostrils of the masks.) Y'all love that, doncha? (chuckles) So, we got ourselves a deal? (The Voodoo Masks glance at each other. Then the leader opens his mouth and a horde of black, ghostly Shadow Demons flow out. Facilier cackles.) NOW WE'RE COOKIN'! We're gonna find ourselves a frog! Search everywhere! The bayou, the Quarter. Bring him to me alive! I need his heart pumping... for now. Alle! Tout de suite! (Facilier laughs evilly as the Shadow Demons leave on their search for Naveen.)
Dr. Facilier stepping on and killing Ray. Disney managed to make killing a bug incredibly cold, brutal, and horrifying. To top it off, Ray was the comic relief.
When Ray is stepped on, he makes a distinct sort of... squelching noise.
And Facilier's face as he did it. He's one of the only Disney villains to kill off a character- and one of the only to kill off the cute animal sidekick.
When Facilier is holding a little voodoo doll of Daddy La Bouff, he's also holding a needle, which he slowly ebbs closer and closer to the area where the doll's heart would be...
The same horrifying suspense during the would-be wedding between Charlotte and "Naveen" on the float.
The fact that Charlotte almost married an imposter (who is actually a much-older and uglier man, just to rub it in further), and thus would've lived out her life in a false relationship had the plan succeeded, is horrifying on multiple levels.
The jar in Mama Odie's house that contains her eyes and teeth. Even the protagonists do a double-take and cringe.
The eyes even seem to follow everyone as they walk, raising plenty of... just plain weird implications.
"ARE YOUREAAAAAAAA-DY!!??" Facilier getting dragged away was mildly unsettling, but the SCREAMING FACE ON THE GRAVESTONE!
The chanting is quick and if you're not listening closely, it can sound like they're chanting "HUNGRY" instead. All in all, Facilier's death is arguably one of the most disturbing Disney has ever created.
Facilier's reaction. He first says a Little "No", and then says a Big "NO!", while he frantically tries to put the medallion together and beg for another chance. He even tries to grab the ground for a handhold before he's finally pulled in.
Facilier's shadow minions. The way they move too fast and some of them had freakishly long legs and the screams they use to communicate... *shudder*
What makes it worse is how they can just snatch you up and drag you away... the scary part of it is that they don't even have to grab you. They just have to make contact with your shadow and you'll just be dragged off, not being able to see what it is that has you.
They can also apparently interact with people in other ways, such as Facilier's shadow kicking Lawrence's during Friends on the Other Side. The shadows don't have to be kidnapping anyone to be creepy; they've got plenty of other ways to hurt people without even needing to directly touch them.
When the shadows run through the town, the ones walking on the shadow of the gate make the irl gate lantern bend. And their voice sounds something like a slowed down howl, sped up laughter, and a shriek combined into one. This is what nightmares are made of.
Those demon-spirits most likely took or ATE Dr. Facilier's soul.
A bit of subtle and possibly unintentional Fridge Horror: look closely at where Facilier's standing during the opening moments of his Villain Song. The Operator symbol can be (faintly) seen◊ on the wall outside his door.