Marina And The Diamonds - Electra Heart

Electra Heart isn't a character, and it's also quite hard to call it symbolism. It simply changes as the series goes on, there's no true meaning to it. Notice how the heart gets smaller as Marina realizes her world is crumbling down, but gets bigger as things get better. At the end of this video, she believes her relationship and happiness is over, and she smudges the heart (in one of the few cases, which is really big on symbolism) which shows that it all comes to an end. No one actually dies.