This is based on opinion. Please don't list it on a work's trope example list.
Nightmare Fuel / Melancholia
The opening sequence, which ends with the earth being completely destroyed.
Even disregarding the terrifying climax of the opening sequence it sure doesn't stint on disturbing imagery: The very first shot we see is Justine in her wedding dress, giving the audience a disconcerting Thousand-Yard Stare while dead birds fall from the sky in super slow-motion – quite an opening shot...
Justine's simple, quiet speech on the fundamental evil of life on earth, and the fact that this is the only place in the universe where life is to be found — and soon it will be gone.
The look of sheer panic on Claire's face when she realises that Melancholia is moving towards Earth and not away from it.