Flaky Pastry gives us the goblin vizierReptilis. He finally gets brought to heel, but is more-or-less left in his position of authority because, despite his being an example of this trope, he's still the most qualified candidate available.
Daimyo Kubota is an always plotting, Genre Savvyaristocrat. Almost everything he does to try to usurp Hinjo's position is just plain hateful, culminating in him ordering the assassination of a pair of former commoners who were promoted to nobility. The wife is pregnant. When the plan fails, he murders his own number two with poison just to give himself time to escape. When he's captured, he plans to use his good publicity to avoid justice and humiliate Hinjo. Fortunately, right after he outlines the above plan, Vaarsuvius, not wanting any more distractions from the main plot, disintegrates him. His status as a Smug Snake is cemented by the fact that he just doesn't stack up against Big Bad Xykon and his long-term planning henchman Redcloak. He's also horribly naive, and thinks taking the city back from Xykon will be a trivial matter.
Likewise, Nale, leader of the Linear Guild and Elan's Evil Twin, isn't nearly the Magnificent Bastard and evil mastermind he likes to think he is; Vaarsuvius points out that most of his plans, which he likes to think of as works of genius, are in fact rather trite and cliched (if nevertheless somewhat effective), and he has the tendency to come off as being rather smug rather than magnificent. Elan and Nale's father, General Tarquin, a genuine Magnificent Bastard, more or less confirms this when he is insulted by being compared to Nale:
"Your brother was a disorganized buffoon who cared more about satisfying his own ego than any realistic plan for world domination. All he ever cared about was that everyone knew HE was the victor, even when the situation called for keeping a low profile."
General Tarquin himself also qualifies, despite presenting himself as a Dangerously Genre SavvyMagnificent Bastard (and convincing a fair few readers that this is the case). While he is a lot smarter and more successful than Nale, he really isn't all that different at heart, ultimately being little more than an egotistical sociopath with a massively inflated sense of his own importance and role in the story, as well as a tendency to fly into a murderous rage when things don't go the way he wants them to.
Tsukiko is an incredibly vain sorceress who believes she's the heroine of some Twilight-esque novel with Xykon as the dashing undead love interest. Worst, she actually believes she can treat Redcloak like dirt and constantly get away with it, up to the point of replacing him as Xykon's Dragon. Redcloak ultimately demonstrates that she's very, very mistaken on every count, and way over her head.
Faz in Shortpacked! is a toadying, nakedly ambitious sycophant with a permanent smug expression and a tendency to openly plot against and undermine the people he works with. Absolutely no one in the store, including his boss, particularly gives a damn about his continuing existence or welfare.
Faz: Your thoracic diaphragm heaving in anger is not unlike how I picture your anatomy during our inevitable lovemaking.
If you need even more evidence of his Smug Snake status, just read his entry on the cast page: "Shortpacked!'s most annoying recruit has an infuriatingly smug grin you'd love to remove with a grenade launcher."
It doesn't help that he also comes off as a slimier Casanova Wannabe when trying to convince Amber to sleep with him, including pulling out the Kinsey Graph when Amber said she was a lesbian (Long story)
He's obliviousness over the fact that Amber was really his half-sister isn't helping his case either.
Vriska Serket of Homestuck. She's a spiteful, conniving, BLUH BLUH HUGE BITCH with a serious case of Chronic Backstabbing Disorder. She also would like to think that she's the best Troll, but really isn't capable of manipulating anyone without resorting to Mind Control, and usually ends up being manipulated herself by other characters' Batman Gambits.
She's later one-upped in her smugness by her ancestor Araena who puts on a show of being nice and courteous, but is actually a Glory HoundKnight Templar who thinks that she's the only one who stop Lord English because she's smarter than everyone else. Ironically, seeing what a horrible sociopath Araena is (and how horrified everyone else is by it) causes Vriska to realize how awful she's been to her own friends.
Sluggy Freelance: Ralfoy Malfoy note a parody of Draco Malfoy. He takes the smug-snakeness to the extreme by acting smug even though his "enemy" is the adult but childish Torg who will inevitably just do something like give him a wedgie (or even tell him to do it himself) and send him scuttling away. Only in the 3rd parody did he actually manage to rise to the status of a real adversary for a while... and that was at the expense of getting a video put up on YouTube of him sayinghe thought a ferret was sexy-cute.
Umbria/Zaedalkaah from Our Little Adventure. She believes herself to be a skilled liar and cunning calculator, but most of what was actually going in her favor is simply luck. She used to be a skilled half-demon assassin, but has been reborn into something considerably less powerful. It doesn't make her act any less entitled however...