The Harley Quinn comic book showed the "business side" of being a henchman in Gotham City, as Harley held auditions. (Looking, like most Bat Villains, not just for muscle but stylish muscle). The group she wound up with, the Quinntet, were all veterans of other Gotham villains' gangs, and discussed it almost as if they'd been in theater productions.
Streets of Gotham loves this trope, as it has already introduced an affably villainous 'just business' realtor-to-supervillains, and a carpenter, both of whom work on the utmost principles of discretion.
In Birds of Prey, Huntress and Black Canary go disguised as former minions of Penguin and Riddler to a large meeting of Gotham's hired muscle. It turns out, rather than planning some massive heist as they originally thought, the guy who called them is actually trying to form them into a unofficial union in an effort to get better pay and treatment from the main villains who hire them.
The Deadpool comic book upgrades the faceless minions of HYDRA into Punch Clock Villains, mostly through the info we receive from Deadpool's kidnapped pet minion Bob, Agent of HYDRA. Through him we learn that some of the minions of HYDRA doesn't care about the take over the world agenda, they just can't find work anywhere else. They also fear and hate Captain America, Elektra and Wolverine. However, one downside of working for HYDRA is that they don't get dental insurance.
Deadpool himself once stopped midway through a fight with Spider-Man when he realized he was off the clock. Though villain is a pretty harsh word, considering the fight at that point had degraded to a Yo Momma contest.
In the first issue of the The Invisibles, King Mob kills a whole slew of security guards while trying to break Dane out of a juvenile facility run by the Archons of the Outer Church. About twelve issues later, we see the life of one of those security guards — his family, his relationship with his wife, his time in the military — up until his death at King Mob's hands.
The Shocker, an unfortunately namedSpider-Man villain, differs from his peers mainly because he considers supervillainy more of a job than a way of life. He is essentially a gifted inventor that considers robbing banks to be more entertaining than a typical desk job, and has taken pains to avoid causing casualties in the past. Later, he starts working for Hammer Industries, which hires him out as muscle, where he punches into work and has a supervisor, etc.
The Sandman, another Spidey enemy, is, while a supervillain, still a halfway decent person, who, among other things, changed his real name so that his mother wouldn't get caught up in his criminal career. He even tried a heroic career, and kept it for quite a while before the Chronic Villainy set in, and he's still shown to be a relatively amiable person once you get past the life of crime, and is noticeably less violent and cruel than his peers in Spidey's Rogues Gallery. He occasionally gains traits of an Anti-Villain as well, especially in Spider-Man 3, where he was a full on Anti-Villain who only commits crimes to save his daughter. In the early Marvel days, Sandman and Ben Grimm ran into each other in a neighborhood bar. They put down some minor troublemakers who were disturbing the peace, then spent the rest of the afternoon sitting side-by-side at the bar, swapping stories over beers.
Recurring minor Invincible villain Furnace. In his later appearances, he wants to kill Invincible for damaging his suit to the point that it required massive repairs, setting him back millions of dollars and forcing him to start at square one. "I'm just trying to make a living, he has no idea how expensive this thing is..."
One of the concentration camp guards in Maus is shown to be surprisingly affable, acting friendly with prisoners and reminiscing about beautiful countrysides. When one day he comes to work incredibly chilled and frightened, acting harshly with the prisoners, Vladek guesses that the guard witnessed a mass killing since he was stationed for a time at Birkenau (or Auschwitz II) before coming back.
Ron Gomz in Doom Patrol was hired by the team's benefactor Thayer Jost to take them on as a publicity stunt... but when he attacks and finds out they cancelled their contract with Jost (and consequently he wasn't going to get paid), he had a bit of a meltdown of properly villainous proportions.
The Human Flying Fish from the latest Aquaman series. As he says, he's just a wage slave doing his job: they design the suit, they get to pick the name and the color scheme, he gets to beat people up.
The new Big Wheel in Ghost Rider, who even goes so far as to say "nothing personal" and that this is just work for him.
In Little Gloomy, Simon von Simon's hunchback assistant Boris honestly couldn't care less about whatever project Simon is working on; he's a hunchback, so mad scientist lab assistant is the only job he can really get. He also tells Frank that he's just doing his job before hacking him to pieces with an axe. When Simon's castle blows up, not only is Boris long gone (the gig was clearly going sour), his first thought is sifting through the newspaper's want ads for new employment.
Atomic Robo portrays most German soldiers this way, making sure that the readers see them as human beings.
German who just came face to face with a ticking bomb: "Dammit, I don't even like Hitler."
Eric Finch from V for Vendetta could be considered to fit into this category, depending largely on one's political perspective.
Most of the thugs, minions, and lackeys in Empowered are pretty decent guys, especially the protagonist's boyfriend and his buddies. The segment where he explains that killing superheroes is even dumber than killing cops is hilarious, and makes an enormous amount of sense.
In the Evanier/Spiegle run of Blackhawk, Professor Merson is an American scientist who designs wonder weapons like the War Wheel for the Nazis. But only because they pay him. After finally being captured by the Blackhawks and in British custody, Merson happily switches sides to work for the Allies after Winston Churchill offers him more money.
Spoofed in a The Far Side comic, where a series of woodland creatures are shown lining up at a pair of punch clocks, labeled "Predators" and "Prey" respectively.
When the Thunderbolts were turned over to HAMMER in the wake of Dark Reign, one of Norman Osborn's immediate hires was Paladin. Paladin has made a name for himself in the Marvel Universe as a reliable mercenary who gets the job done and doesn't ask questions, and he stays true to that reputation for much of his tenure with the team. He knows Osborn is crazy and that what he's doing is wrong, but, well, as long as there's money, you know?
Neil Gaiman offered some examples in his The Sandman comics. Most notable is Cain, who routinely and casually murders his brother Abel. In The Wake it is revealed that Abel is a dream; Cain murders him over and over because it's his gig, and he has a contract that says so.
While he does have a contract, it's rather strongly implied that he suffers from some sort of compulsion, unless his promise to "do 'it' less often" when he gives Abel a new pet gargoyle is standard abuser behavior. Either way, he leans into Psycho for Hire territory.
While Cain indeed has a contract, it didn't begin his role as the First Killer, only affirmed it. He keeps killing Abel bacause that's what he is, and that defines him. If he stopped, he would no longer be Cain, and would cease to exist. For him, anything is a reason to kill Abel, including being bored. The contract is just an extra justification.
Transformers: More than Meets the Eye: Five random Decepticons have become a crew called the Scavengers, and they meet a sixth on a planet littered with corpses from the war. They sit around a fire and express wonder at the idea that the war is over, and now they don't know what to do with their lives having fought for so long. They lacking the sadism and ambition that make up most Decepticons, so they opt to head home and take it from there, and then they nonchalantly execute the Autobot they found alive in their fireplace. Later, when they meet a brain-damaged Grimlock, they take him with them, since the war's over and they figure whoever's in charge, Grimlock being with them increases their odds of coming out looking good.
X-Factor during Peter David's first run, a villain named Random trashed most of X-Factor as well as the illegal foreign immigrants they were protecting, without breaking a sweat. Then he casually mentioned he was getting two grand to return the X-Patriots to their country of origin, which is all he cared about, as a working stiff. Havok pointed out that X-Factor were working stiffs two, and wrote him a check for four thousand on his government expense account, and the battle was concluded amiably. "Pleasure doing business with you.