Nina Dobrev's career is thriving, with one movie out so far this year and four more in post-production. After beginning her career in 2006 with her role as Mia Jones on Degrassi: The Next Generation, she has consistently found work in film and television, showing off a remarkable amount of range. However, she may always be best remembered for her time on The Vampire Diaries.

Dobrev lead the show in her role as Elena Gilbert, but she also played three other doppelgangers, including Katherine Pierce. Where Elena is meek and needs protecting, Katherine is willing to do whatever it takes to get what she wants. However, this could only last so long, and Katherine ended up dying in season 5, with a brief resurrection in the finale. Her downfall had immediate and long-term causes, but the most significant one was the people around her, who dismantled her carefully-constructed defenses.

Elijah Mikaelson

Given their flirtatious relationship in the 15th century, Katherine believed that Elijah would do what was in her best interests. She relied on that belief as she tried to negotiate her freedom from Klaus, but Elijah betrayed her, believing that he couldn't trust her and wanting to rebuild his relationship with Klaus.

If Elijah had helped Katherine gain her freedom, she likely would have happily moved on with her life. She was a flirt and got into mischief, but most of her actions were intended to keep herself safe. By failing to protect her from Klaus, Elijah forced Katherine to take desperate actions, which led to her death.

Nadia Petrova

Nadia captures Katherine in The Vampire Diaries

While Silas was trying to track Katherine down, Nadia assisted him, though she admitted she had her own motivations for doing so. She wanted to get to know her mother and know why she had never come back for her. While this was understandable, it did end up helping Silas find and nearly kill Katherine.

In addition, Nadia was the one who figured out how to transport Katherine into Elena's body. It's difficult to say which of her many crimes got Katherine sent to Hell, but the body-snatching likely had something to do with it. Had Nadia stayed away or been more careful, she might have been able to either keep Katherine safe from Silas or at least grant her a happier afterlife.

Damon Salvatore

Katherine and Damon talk in The Vampire Diaries.

Damon offers Katherine to Silas on a silver platter, which was certainly a stepping stone to her ultimate death and destruction. The two of them had a very passionate dynamic, alternating between love and hate, but offering her up as a bartering chip was unnecessarily cruel.

Though he didn't personally play a part in either of her deaths, that wasn't for lack of trying. He bit her and offered her blood to Silas, wishing her goodbye as he did it. His intention was to kill her, and the fact that it didn't work immediately doesn't get rid of the fact that the loss of the Cure did eventually kill her.

Mr. Petrova

Katherine's Parents Taking Her Child Away On The Vampire Diaries

Fans know very little about Katherine's father, but like most TVD parents, he is partially responsible for the monster his daughter became. After giving birth to Nadia, Katherine was sent to England, where she ran into the Mikaelsons. Had she not been seen as such an embarrassment, her life likely would have been uneventful.

In that possible world, Katherine might have had the chance to have a real relationship with her daughter. She is responsible for her own actions, but had she stayed in Bulgaria and avoided the Mikaelson brothers, she probably wouldn't have felt the need to reshape every part of herself to be a survivor.

Klaus Mikaelson

Klaus and Katherine looking at each other

Klaus's actions toward Katherine caused her to become a vampire, led to her centuries of running, and transformed her from a flirtatious but ultimately ordinary woman to one who would do anything to survive. While he was not part of either of her deaths, he was responsible for turning her into the villain she became.

Had Klaus not tried to kill her, Katherine likely would have lived out a normal, human life. It might not have been quite so exciting, but her Traveler heritage means she may have found her way to power another way. Even so, she wouldn't have lived long enough to even meet the Salvatore brothers, ensuring a much less violent ending.

Silas

Paul Wesley as Silas in the Vampire Diaries

Seasons 5 and 6 showed off how dangerous Silas was and how evil his plans were, and his main target for much of that time was Katherine. Because she had the Cure inside of her, he intended to kill her in order to take it for himself. By all rights, he should have killed her by draining her of blood, but her survival only meant a more extended death.

The creation of doppelgangers and the Cure went back to Silas, and his choice of Amara over Qetsiyah was the original sin that caused all of Katherine's suffering. In a number of ways direct and indirect, Silas ruined Katherine's life and initiated her death. The only reason he isn't more responsible for her death is that he didn't actively kill her himself.

Elena Gilbert

Image of Elena Gilbert and Katherine Pierce lying on the floor in The Vampire Diaries

The beginning of the end for Katherine was when she became human, a transition that Elena was directly responsible for. After Katherine attacked her, she forced the cure down her throat, which led to Silas's attack and Katherine's rapid aging.

In addition, the greatest threat that Elena had for Katherine was how much she was loved. If not for Elena, Katherine might have been able to win one of the Salvatore brothers to her side, and she certainly would've had less resistance to her plans. She was killed for taking Elena's body, so if the others hadn't loved Elena as much as they had, she might have had a new body without too much struggle.

Bonnie Bennett

Bonnie was dead for a considerable chunk of season 5, so she wasn't involved with Katherine's first death, other than being used as a bargaining chip by Silas. He offered her resurrection if Damon brought him Katherine, and it worked.

However, Bonnie had a major role in Katherine's final defeat. After emerging from Hell, Katherine attempted to destroy Mystic Falls. Bonnie was the one to redirect the hellfire, sending it straight to hell while Stefan ensured Katherine was sent back as well. Though she did it to save Mystic Falls more than to punish Katherine, Bonnie did end up making the move that finished off Katherine Pierce for good.

Stefan Salvatore

Stefan and Katherine die in The Vampire Diaries

While Stefan was generally neutral toward Katherine, his love for his friends and family caused him to make two key moves against Katherine that sealed her fate. When she had control of Elena's body, he stabbed her with the Traveler knife, thus directly causing her death. Then, when she returned to destroy Mystic Falls, he made sure she was consumed by Hellfire.

Of all Katherine's flirtations, her feelings for Stefan seemed the most genuine, perhaps because of their doppelganger connection. Given this, she allowed herself to be vulnerable around him. While he rarely took advantage of this, he was willing to do the necessary dirty work to stop her worst crimes.

Katherine Pierce

Katherine Pierce in The Vampire Diaries

At the end of the day, the one most responsible for Katherine's downfall was herself. Nobody can blame her for doing what she had to do to survive, but she took it much further than that, playing games and causing torment to the people around her. While she was innocent when Klaus first came for her, she caused every other enemy she had to face.

The villains on The Vampire Diaries have a lot of chances to find redemption, and Katherine even seemed like she was heading down that route until she gave in to her darker instincts. Had she not woken Silas, the Cure wouldn't have been a threat to her. Had she not tried to kill Elena, she would have stayed a vampire without having to worry about death. Had she not taken Elena's body, she might have found Peace. Though others played a part, Katherine was always the architect of her own destruction.

NEXT: 9 Similarities Between Elena & Katherine On The Vampire Diaries