Playing With / Apocalypse Maiden

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.
Back to Apocalypse Maiden, there might still be a chance to save both her and the world.
http://tvtropes.org/pmwiki/pmwiki.php/PlayingWith/ApocalypseMaiden