At first glance, Klaus seems to be a villain — killing without a thought and pursuing his enemies relentlessly. But when we learn more about him and his past, we realise that he is nothing but a broken man desperate for companionship, loyalty, and love. Growing up, Mikael ruthlessly abused Klaus physically and emotionally for being foolish, impulsive, and weak. And once Klaus's true heritage is revealed when he activates his werewolf gene, his own mother shuns him after magically suppressing his werewolf side. His turn towards power and self-preservation was born out of his parents' torment and rejection of him.
Nobody is born evil. Klaus was made to be evil by the 1000 years of betrayal and abuse he suffered as well as the persistent loneliness and abandonment he experienced. His psychological scars are what ultimately transformed him into a merciless monster. Throughout the TVD franchise, we even get glimpses of goodness in him., but because of his belief that love is a weakness, he tries to hide how he feels out of fear that his enemies would use it against him. In the end, he's a misguided villain with a soft side prone to obsessions and insecurities.