The Vampire Diaries set up human Elena with a classic love triangle between vampire brothers Stefan and Damon. Elena eventually ends up with Damon, best known for his piercing gaze, dry humor, and his total disregard for feelings until he can manipulate them.
His selfish attitude and disregard for others are a result of a history of heartbreak, betrayal, and unrequited love, but that doesn't excuse these behaviors. His refusal to take responsibility for his actions, apathy towards human life, and his dismissal of emotions are all things he excuses as a vampire, but in reality, make him terrible to be around.
In the pilot episode of The Vampire Diaries, Damon is introduced as a cold-hearted, antagonistic, vengeful monster. Of course, he is one -- fitting right into the stereotypes of a broody leather jacket-wearing, modern vampire, although not quite the romantic version of the late-aughties he becomes.
Instead, he embodies the scary monster vibes associated with classic vampires hypnotizing and feasting on humans. Strength, power, and a total disregard for the sanctity of life. He has no remorse for killing his victims. In fact, he treats killing them as a bonus to making his younger brother's life more difficult. He's gleeful about the prospect of killing the people of Mystic Falls.
When Damon says this to Isobel in season 1, episode 21, it's easy to overlook the blameless part of "shooting the messenger." Of course, Isobel's not blameless when it comes to the complications of the Salvatore family. However, it’s pretty clear- this isn’t Damon’s first time threatening to kill the messenger.
In a little twisted way, this could be seen as romantic since Damon is defending Elena. Instead, Damon's playing out his power control battle set up around Stefan, Katherine, and the other vampires that Elena had no control over being thrust into. His actions demonstrate he has no issue putting the blameless into this fight if it means he gets his way.
In season 2, episode 12, Damon's full of indifference towards his previous romantic partner, Rose as she's dying. Elena sees this major red flag and expresses her discomfort at his lack of an empathic response. Even though Damon claims to care deeply for Elena, he makes a joke about her feelings.
His use of deadpan humor is because wants Elena to see him in a positive light when being honest about his emotions would be far more successful. Instead, Damon's need to not feel emotions himself once again makes him out to be a callous jerk. A being with good intentions wouldn't be snarky about how long it takes to die. And especially not because the atmosphere’s depressing.
In that same episode, after Damon's relatable confession that feelings hurt, he attacks a woman to feed on her. In regards to Damon's true nature, it's telling. Admitting that he's going to kill her because he's not human is Damon excusing his behavior. Other characters manage to sustain themselves without murder- and without playing with their food.
Damon expresses his regret to Jessica as she’s under compulsion, But his choice to release, then attack her is a sign that he takes no responsibility for his behavior. He may have regret for his actions, but he chooses to terrorize and harm for his personal benefit.
Damon continues to shift responsibility for his actions, and in season 3, episode 15, he uses Elena's rejection to excuse his behavior. Even after he admits to having feelings for her and wanting her to choose him over his brother, he shrugs it off with yet another acknowledgment of how his behavior isn't good enough for her.
Damon recognizes that his pattern of behavior alienates him from the people he cares about in Mystic Falls. But he continues presenting the front that he doesn't care about any of them, downplaying their responses to his bad behaviors. His choice to not adjust his behavior is a red flag.
Damon is a loud supporter of the vampires' ability to shut off all connections to human emotion. After Elena is turned and chooses to shut off her emotions, he gets a taste of his own callous medicine. Then he takes that choice away from her in episode 21 of season 4, by murdering her brother in front of her.
The decision to taunt Elena with her brother's death is another example of Damon's disregard for the emotions of others. In snapping Jeremy's neck, he mocks not only Elena's emotions about her brother but also Jeremy's positive reputation. Even though his actions do succeed in Elena reconnecting her humanity, he goes about it in an overly cruel way.
During Damon’s spree while craving vampire blood thanks to the ripper virus, it's evident that Damon takes pleasure in harming others. In season 5, episode 15, Damon expresses no regret for his actions. Instead, his frustration is from not being allowed to go hunt down Katherine for revenge.
While vengeance is understandable, the fact remains that Damon used his vampirism as his reasoning behind hunting humans. By that logic, Damon's vampire-hunting spree is murder. He's been hunting and feeding on his kind with no remorse. And here, he's admitting to his murderous tendencies without a shred of remorse for those he's killed. Instead, he focuses solely on getting to continue his violent streak.
Even in his darker moments earlier in the show's run, Damon seems to try to have Elena's best interests in mind. Fighting his feelings for her, insisting he wasn't right for her, and toying with her emotions again, Damon claims to love her. But in season 6, episode 6, he complains to Stefan about Elena's memory being wiped.
Looking past the fact he's complaining about this to a guy who was also in love with Elena, Damon ignores her happiness. He scoffs at it, in a manner a little too close to "If I can't, no one can" for comfort. He disregards the times he's told her to be happy without him and is frustrated when she does.
Damon denies even more of his emotions during season 7. In episode 5, Bonnie points out some similarities between Lily and Damon, and when Damon uses this argument to justify his past behaviors, he's only half-joking. It's true Damon likes his kills count to be a little more bloody and a little less brainy compared to Lily's preferred emotional torment.
But Damon's long-term relationship with dismissing emotions is something he doesn't seem to want to get over. And using his habit of hurting people face to face versus more underhandedly doesn't make up for the fact that he still likes to hurt people.
The final season of The Vampire Diaries may end with Damon and Elena riding off into the sunset, but it's also still pretty clear that Damon doesn't actively think about taking responsibility for his actions. Even though he tries to compel Stefan to protect him, he does so while ignoring Stefan's desperate desire to do the right thing for the people he's harmed.
Stefan’s ownership of his actions and emotions has led him to do better and try to protect the people of Mystic Falls. Damon's choice to make the same sacrifice is motivated by his desire to protect his brother, not to atone for the years of pain and suffering he's inflicted.