Klaus & Katherine - My Passion (Story in the description)

Story: Klaus meets Katherine, the doppelganger of the original Petrova and wants to use her in order to break his curse but he's impressed by her and eventually they fall for each other. After a while Katherine understands that he's a vampire and what he wanted from her and they fight. She rejects him, hi hits her and hee gives her his blood to cure her but she still thinks he wants to sacrifise her so she kills hershelf, completes the transformation and runs away. He feels betrayed and he kills her family to get revenge. They both turn of their "human" part and become monsters. After years the meet again in Mystic Falls. Klaus captures Katerina and tortures her in every possible way, physically by hurting her and psychologically by flirting with Greta. Katherine kills Greta and runs away once again. Klaus goes after her and finds her with Stefan. He's jealous and he hurts him, so Katherine understands that after all these years he still loves her. When Klaus breaks his curse, Bonnie tries to take Klaus down but Katherine has realised her feelings for him, she kills Bonnie to protect him and they end up together.