This is based on opinion. Please don't list it on a work's trope example list.
Nightmare Fuel / Crowns of the Kingdom
Maleficent's spell that starts the whole story. It's described in great detail, and its effects nearly doom all of Disneyland.
The realm of Inpotentia, a place where discarded, forgotten, or unthought of ideas go. Characters trapped in there have to remind themselves who they are every second or else they'd disappear completely.
The Dispirations, creatures who are unspoken and forgotten thoughts given being. One tells Maleficent that there are countless numbers of them.
Mickey and Donald nearly drowning while being attacked by Dispirations in the Submarine Lagoon.
The Disney Villains summon Chernabog. He proceeds to nearly wipe out the park before being stopped.
The final battle with Maleficent has her nearly kill Mickey at several points.