Because I'm Good At It

"I detest violence. It's a pity I'm so good at it."

- Colossus, X-Men Noir: Mark of Cain

Someone has a less than morally sound job, like a drug dealer, arms dealer, assassin, or lobbyist. They usually get into the job to make ends meet, especially if the job is illegal, but when they become financially sound or even get a legal job, they refuse to stop. Why? -- because they're good at it. The fulfillment of being competent has surpassed the fulfillment of being a "good person." Or, they're willing (if in a legal job, like lobbyists) to let their job damage their personal lives and public facade for the simple reason of competence.

See also Do Wrong Right and Punch Clock Villain. Compare Evil Virtues. Contrast Reluctant Warrior, who fights because he has to... and isn't that good at it.

Comics

 * Mr. Nice from The Batman Adventures is basically Ned Flanders, except he wound up becoming a master criminal because he is incredibly good at it.
 * Lobster Random claims to be a professional torturer because he's good at it, understands it and can't do anything else.
 * Nexus spent most of his career bitterly miserable that a Sufficiently Advanced alien was compelling him to travel the universe executing mass murderers. The oppressed cheered him for it and tyrants loathed him for it, but Horatio himself just wanted to stop killing people. When, after years, he finally gets his wish—the above-mentioned alien agrees to leave him alone, and another member of the alien's race agrees to maintain his super-powers—Horatio realizes that he's spent his entire adult life doing this, and executing murderers is the only thing he knows how to do.
 * Occasionally Bruce Banner is called out on the fact that, despite having an intellect on par with Reed Richards or Tony Stark, before becoming the Hulk he devoted his life to making bombs. His explanation? He was good at it. And indeed, he made the most destructive bomb ever; one that never stops exploding. The Hulk.

Film
"Neil McCauley: I do what I do best, I take scores. You do what you do best, try to stop guys like me. ... Vincent Hanna: I don't know how to do anything else. Neil McCauley: Neither do I. Vincent Hanna: I don't much want to either. Neil McCauley: Neither do I."
 * Thank You for Smoking: Nick Naylor is a lobbyist for tobacco companies and invokes the trope by name in the movie (and the book?). He even associates with similar lobbyists (NRA and the alcohol lobbies) and discusses strategies and a viewer can tell that these people take pride in their work (at one point they're deeply insulted when Nick declares that only he would be hunted down by vigilantes for what he does).
 * Well, only he was.
 * Yuri Orlov from Lord of War is an illegal arms dealer who has several reasons to quit - his wife threatening to leave him, a Interpol agent dogging him, and building a successful lumber export company, but goes back to arms dealing because, at the end of the day, it is what he's good at.
 * Famous dialogue between a cop and a big-time robber in Heat:

"Abby: That's messed-up."
 * Elektra gives this as the reason for being an assassin when Abby asks.

Literature
"He took no pleasure in being a thief, but he took great pleasure in being a very good thief."
 * Raymond E. Feist's Riftwar Cycle describes Jimmy the Hand thus:


 * Honor Harrington: Honor does what she does because she's "better at it than most other people" (almost direct quote from the book). Given as what she does is lead fleets into battle, and almost always wins, it might count. It's clear that she doesn't like it, just that she's very capable. She might not like the idea of killing hundreds of people on both sides in her actions, but even she admits at times that she enjoys the thrill of battle, especially if her target is someone who deserves it. Her own husband calls thinks of her as the Handmaiden of Death.
 * In The Lies of Locke Lamora, the Gentleman Bastard Sequences don't do anything with the huge amounts of money they acquire from their long cons. It just sits there. But they are excellent thieves, so why would they give up?
 * In Dorothy L. Sayers' Gaudy Night, Harriet Vane discusses how she continued to write murder mysteries after being tried and acquitted for murder; she says that anyone with feeling would rather scrub floors, but it happens that she would scrub floors very badly and writes mysteries very well.
 * In The Godfather Returns, the Interquel to The Godfather, Vito Corleone is suggested as following this trope. During a flashback history lesson, the book discusses Vito's early days as Don. While his children were still growing up, Vito used his Genco Olive Oil delivery trucks to deliver alcohol during Prohibition, amongst other things. As Prohibition came to an end, Sonny and Fredo had joined "the family business".

Even so, he had amassed millions of dollars: A staggering amount of money in the 20's and 30's that would let him and his family live in comfort for the rest of their days. Instead, he tried to form an alliance with Maranzano, the kingpin of New York. Maranzano refused, beginning the Castellammarese War that ended up Vito as the undisputed head of New York's underworld. Vito had made his fortune without stepping on anyone's toes and had sworn that his children wouldn't have to follow in his footsteps.

With such a fortune and his own wits, there were any number of legal businesses and ventures he could have undertaken. However, the book suggests that once Sonny and Fredo were part of his business, he had to continue on the path he's chosen. Not only because he was so good at it, but because his two oldest sons were not good at anything else. Left on their own, with no supervision or protection, no real skills or education, and a criminal mindset, Vito felt they would both be dead within a year.

This is also why Michael stays with gangstering later books. He keeps insisting he's somewhat ashamed of the family history and keeps wanting to go legit and "they're always pulling him back in", but the fact is he's really good as a ruthless criminal mastermind.
 * In the Discworld novel, The Light Fantastic, there's a master architect. Every time he makes something, the person who hired him to do it maims him in an attempt to make sure nobody ever makes anything better. He doesn't get a less dangerous job because he's good at it.
 * Fisk, in the Knight and Rogue Series is a good-hearted fellow who got into the con business to try and support his sisters, and since he's such a natural at coming up with unbelievable bull on the spot, kept with it. Until he got saddled with Michael, that is, and even then he still gets away with plenty of well woven lies and card tricks.

Live Action TV

 * Nancy Botwin from Weeds is much the same in her career as a marijuana dealer.
 * Or at least she thinks she is.
 * Better Off Ted: The case for most of the main cast, especially Ted, who's especially adept at his job and serves the morally questionable conglomerate Veridian Dynamics despite his otherwise squeaky clean morality.
 * Law and Order: Criminal Intent: One episode featured a handwriting expert who used his skills for nefarious purposes, "because I'm brilliant at what I do!". The expert was played by one Stephen Colbert.
 * Breaking Bad has this as one of the motivations for Walt's actions why he keeps cooking meth.
 * In the Doctor Who serial City of Death, the Fourth Doctor and Professor Kerensky debate the ethics of messing with time, and the Doctor replies, "Well, I'm a professional; I know what I'm doing." Then again, the Time Lords are professional time-travelers who make sure that the timeline doesn't get too screwed-up.

Video Games

 * Metal Gear Solid: At the climax,  laments that fighting was and is his only talent in life, but has some reconciliation in that he never sold out his beliefs and fought for a cause he felt was unworthy. This is a deliberate, non-callous comparison to Solid Snake at this point in the series, who is an even more gifted warrior yet has always blindly followed orders without philosophy.

The plight of those who are natural soldiers versus the concept of peace is one of the oldest and most important themes in the series. Solid Snake is loath to admit it even under the most excruciating duress, but he loves battle, and while his enemies often seek the proliferation of worldwide conflict for the benefit of natural-born soldiers like himself, he has a selfless moral instinct which forces him to stop them at any cost. The secondary plot line of the series follows the journey of his father, Big Boss, which sees him face the same quandary yet reach a completely different conclusion.
 * Zevran from Dragon Age notes that even if he wanted to be anything other than an assassin, which he doesn't, he has been doing this work all his life and doesn't know how to do anything else. Well, nothing else that wouldn't get him arrested for performing in public.
 * Isabela in the sequel gives this as an excuse for her continued career as a pirate (other than simply enjoying the freedom that comes with it), though other characters have pointed out that her skills could easily be put to use doing something else, and unlike Zevran, she chose to become a pirate and there's no one threatening to hunt her down if she quits . One could make the case that this actually makes her come off as much more selfish, given how easily she can ignore the people her actions hurt.

Web Comics

 * Thief from Eight Bit Theater originally took up stealing in order to pay for his father's medicine, then kept stealing even after the situation was resolved.

Web Animation

 * Accuser: When interviewed by a reporter who described his recently acquitted client as a "racketeer and reputed killer", Amoral Attorney Dan Mason claimed he did his job and was "proud of it". His wife even complained he was "too good".

Western Animation

 * In The Simpsons, Krusty the Clown once manages to refresh his comedian routine by starting to complain cynically about the modern world, and becomes popular as a stand-up act again. Soon, however, he's once again persuaded to start endorsing a product even in his act in the middle of complaining about everything else, immediately losing his credibility. He doesn't regret it, though, because as he explains he's realised his real talent isn't comedy - it's selling out.
 * Xiaolin Showdown: Subverted when Jack Spicer quits being evil only to turn back again when he is afraid he'll actually be worse at being good than he was at being bad.