On The Vampire Diaries, if any of the Mikaelson siblings could be considered "the nice one," it would be the always polite -- even when he's ripping someone's heart out -- buttoned-down, impeccably groomed, Elijah (Daniel Gillies). He remains devoted most of all to his brother Klaus (Joseph Morgan) for 1,000 years even at the expense of his happiness. The depth of the Mikaelson's familial dysfunction surpasses that of the grimmest Shakespearean play.

Elijah doesn't always play well with others, especially if it means breaking Rebekah (Claire Holt) and Klaus' bond of "always and forever." Here are five times Elijah is a stand-up guy, and five times he's not.

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Bad Guy: Elijah Decapitates Trevor

Elijah holding a wooden stake on The Vampire Diaries

The Vampire Diaries season 2 focuses on Klaus' mission to break the curse that keeps his werewolf side dormant.  Fugitive vamps Rose (Lauren Cohan) and Trevor (Trent Ford), who have both been on Klaus' bad side for 500 years, hope to use Elena (Nina Dobrev) as a peace offering, handing her over to Elena's"worst nightmare," Elijah.

Elijah's arrival jump-starts the Originals mythology. Loyalty and courtesy are of paramount importance to this Original, and he tolerates nothing less, leaving Trevor without his head and Rose to grieve. Elijah's debut introduces an immortal with an appreciation for the finer things -- a minion with manners.

Good Guy: Elijah Strikes A Deal With Elena

Vampire Diaries Elena and Elijah

There's never any question Elena will come face-to-face with Klaus, but Elijah strikes a deal with Elena that allows her to have some control over her fate: Elena goes about her life business as usual, and he'll keep the ones she loves safe.

Granted, using Elena as leverage to lure his reclusive, paranoid brother out from hiding isn't entirely a win-win for Elena. There is surprising mutual respect between Elena and Elijah, making it hard for viewers to fully accept him as a villain, particularly when he says he's going to kill Klaus. This discord between the brothers would appear to put Elijah firmly on Team Elena, meaning all Originals can't be so scary, right?

Bad Guy: Refuses To Kill Klaus

The Vampire Diaries Klaus Elijah

It turns out blood is thicker than water. When the time comes for Elijah to keep his word and kill Klaus, he bails on the plan. Klaus' promise to reunite Elijah with the rest of their family is too good for Elijah to pass up, but it leaves Elena and her pals in a serious lurch. It also dings Elijah's credibility as a man of his word. Elijah knows the threat Klaus poses once he unleashes his werewolf side which makes Elijah's actions not just reprehensible but stupid.

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Good Guy: Elijah Saves Damon

Elijah choking Damon on The Vampire Diaries

Elena's pact with Elijah is a fortuitous one since a pack of werewolves shows up in Mystic Falls, posing a credible threat to Caroline (Candice King), Stefan (Paul Wesley), and Damon (Ian Somerhalder). When she-wolf Jules (Micheala McManus) holds Damon captive, torturing him for information and threatening his life, it's Elijah who arrives to save the day.

Elijah continues to stay true to his word even though Damon and Stefan can't shake or hide their dislike or distrust of the Original brother, Elijah saves Damon's life for a third time, making him far more trustworthy than the Salvatores who are as capable as fighting dirty as their enemies. Elijah's brutality -- he favors ripping out hearts -- is hard to reconcile with his old-world charm which is part of what makes him so simultaneously hard and easy to love.

Bad Guy: Elijah Goes After Elena

Eliljah looking serious on The Vampire Diaries

The agreement between Elijah and Elena is very clear: if the Salvatores step out of line, all bets are off. Well, a dagger in the back during what is supposed to be a civilized dinner meets the aforementioned criteria. Even though Elena isn't in on the plan, Elijah is ready to take her away, never to be heard from again.

But Damon learns from his first two attempts to put down Elijah, and Elena secures her safety by succeeding where others failed. Elijah may have a conscience, but he's still a cold-blooded killer, willing to let Elena die as part of his plan to exact vengeance on his little brother.

Good Guy: Elijah Tries To Secure Safety For All

With Klaus safely desiccating for the foreseeable future, the only thing standing between Elena and peace and quiet is vampire hunter, Alaric (Matthew Davis). Elijah offers her a deal: hand over Klaus' body and he and his siblings will scatter, and Alaric will follow.

Elijah could exact vengeance upon those who put his brother down like a dog, but Elijah's amenable to Klaus' extended time out and looking over his shoulder for 100 years or so. Of course, the best-laid plans almost always fall apart on The Vampire Diaries, but it's not Elijah who drops the ball.

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Bad Guy: Elijah Kidnaps Elena

Elijah and Elena at the door in The Vampire Diaries.

Elena isn't entirely down with the Original witch, Esther's (Alice Evans), plan to kill all of her children since it means Elijah dies as well. Elijah distrustful of his mother confronts Elena who divulges Esther's plan. Offering to help, Elena winds up a pawn in a scheme orchestrated by Elijah.

This situation is FUBAR for so many reasons: Elijah says he admires Elena, she gives him a heads up about impending doom, Elijah is willing to trade Elena's life for Bonnie's (Kat Graham) or Bonnie's mother's (or both) and he's already screwed over Elena once before. This is straight-up, hardcore villainry is out of character for Elijah.

Good Guy: Elijah Teams Up With Damon

With Klaus and Stefan at each other's throats for the better part of season 3, Damon decides to undagger Elijah who is put down by Klaus after his season 2 betrayal. Damon assumes Elijah might turn out to be a valuable ally after all. Elijah continues to be torn between doing the right thing and doing what's best for his family. This time the latter means not falling for Klaus' manipulative promise of a fresh start once again.

Elijah redeems himself for his previous betrayal, and he gets payback for himself and his siblings. He also does a masterful job of blindsiding Klaus and viewers who undoubtedly question if Elijah is his own man or his brother's puppet.

Bad Guy: Elijah Partners With Katherine

Katherine and Elijah kissing on The Vampire Diaries

Arguably, Elijah's decision to partner up with Katherine poses a conundrum: if she's playing him, he's the good guy in this scenario. But Elijah is aware of Katherine's many faults, and he doesn't question her methods for getting the cure which includes feeding Jeremy Gilbert (Steven R. McQueen) to Silas.

When Elijah learns of Katherine's actions, he pouts and he scolds, but in the end, he lets Katherine off the hook. Elijah's willingness to believe the best about those who deserve it the least would be tragic if it wasn't so annoying. Once again, Elena suffers because of Elijah's terrible judgment.

Good Guy: Elijah Convinces Klaus To Embrace Fatherhood

Klaus loves to sire hybrids, but he's less enthusiastic about being a father to an actual child. If it wasn't for Elijah's exhausting, never-ending attempts to turn Klaus into something remotely human, Hayley (Phoebe Tonkin) and her miracle baby would be at the mercy of some very desperate and unsympathetic witches.

This is when the whole always and forever oath begins to come into play, and fans see the dysfunctional family stuff between Klaus and Elijah makes the Salvatore brothers look like the undead version of Leave It to Beaver. Elijah's decisions good or bad all lead back to some screwed up relations he's been stuck with for 1,000 years. Convincing Klaus to be a good baby daddy is the first step towards a kinder, gentler Mikaealson family.

NEXT: The Vampire Diaries: 10 Worst Things Damon Has Ever Done