Apocalypse Maiden/Playing With

Basic Trope: A person who will bring the end of the world simply by existing; the problem is that s/he is also well-known to or even the beloved of the main character.
 * Straight: Rei's sweet little sister Mei is fated to destroy the world.
 * Exaggerated: Mei is such a sweet girl, if not for the fact that she's a Walking Wasteland, attracts hordes of alien bugs, and is fated to destroy the galaxy.
 * Justified:
 * Mei's soul/DNA/whatever is the key to activating the Doomsday Device.
 * Mei is only half-sister to Rei, her father is an Eldritch Abomination. Even if she does nothing, Mei's simply existance cause space-dimensional distortion, breaking the wall between Earth and the Eldritch Location, bringing unspeakable terror to Earth.
 * Inverted:
 * Mei is a total bitch, but since the world will end without her, everyone is forced to protect her and satisfy her callous whims.
 * Mei is a Barrier Maiden-- without her, evils from outside the world will destroy the world.
 * Subverted: Mei might be fated to destroy the world, but the prophecy isn't exactly set in stone...
 * It's only certain part of Mei that is fated to destroy the world. Remove that part, and Mei is free to live her life.
 * Double Subverted:
 * ...but the attempt to subvert Mei's fate is the action that destroy the world.
 * But that part is integral to Mei's being... i.e., her soul.
 * Parodied: After knowing that she's an Apocalypse Maiden, Mei dyes her hair pale blue and starts acting emo.
 * Deconstructed:
 * Being an Apocalypse Maiden makes people mean to Mei, so she decides to fulfill her fated role to make the goddamn pain stop.
 * Since people are mean to her little sister, Rei decided that the world should end and she wholeheartedly supports Mei to carry her role.
 * Rei destroy the world before Mei can enact her role as an Apocalypse Maiden, to save her from the anguish of destroying the world with her own hands.
 * Reconstructed:
 * Rei's love for Mei allows her to endure people's hatred.
 * Rei and the Five-Man Band travels into Mei's soul to destroy the growing soul-parasite that will destroy the world.
 * Zig Zagged: ???
 * Averted: The much-feared apocalypse isn't caused by a single person.
 * Enforced: "The contradiction! The drama! Let's make the hero choose between the world or her little sister!"
 * Lampshaded: "Ending the world?! This little missy here? You've got to be kidding me, dude."
 * Invoked: Karen, an alien from the 26th dimension trapped in this mundane world, goad Mei into destroying the world so s/he can return to his/her origin.
 * Exploited: Emperor Evulz kidnap and Mind Rape Mei into becoming his puppet, effectively keeping the world hostage.
 * Defied: Some pragmatic people seal Mei in a can.
 * Discussed: ???
 * Conversed: ???
 * Played For Drama: Saving Mei from Karen/Evulz/the pragmatic people/her dark side and convincing her that the world is worth living, even if some Humans Are Bastards.

Back to Apocalypse Maiden, there might still be a chance to save both her and the world.