No one likes a backstabber. In storytelling, an easy way to make audiences hate a certain character is to have him/her betray the others, cementing them as self-serving weasels with no regard for their peers. Naturally, this bonds viewers in their collective dislike.
That phenomenon goes double for video games. Within this medium, the story relies entirely on players' skill and effort. Traitors bypass that effort and often set gamers back to a previous point. They're essentially akin to cheaters and spammers in a co-op match. Just take all the frustration that emerges there and apply it to a narrative.
8 Daisaku Kuze - Yakuza 0
This snobby has-been uses the yakuza for position alone. A little loyalist worm, Kazuma Kiryu makes a perfect scapegoat in an underhanded bid to increase his position. When the up-and-comer refuses to take this lying down, it sets off a bitter rivalry that carries through the Yakuza prequel.
Kuze's fellow conspirators try all kinds of offensives against Kiryu, and the thug is always there to personally deliver the blow. What's more is that he repeatedly loses these brawls, adding to the pettiness fueling his character. Kuze is one of those gaming villains who fail upwards.
7 Zeus - The God Of War Series
Zeus is the king of the Greek gods, and he has an ego the size of Mount Olympus. He looks down on mere mortals with disdain, seeing them only as fodder. He covertly helps his son, Kratos, ascend to godhood, but the Spartan spits on the deities' pettiness and holds a grudge for past injustices. This insult, coupled with fear, leads Zeus to strip Kratos of his godly powers and send him to the Underworld.
Needless to say, the former God of War isn't happy and vows vengeance, but it's a vengeance that players have to wait for. Kratos spends two whole games clawing his way back to power and bringing the fight to Zeus. Upon finally defeating his nemesis, the Spartan's revenge is cold enough to savor.
More than that, it feels good sticking it to someone who counts you out. Much of these games are about defying those who think themselves superior. Zeus and his betrayal is the epitome of that concept. It's no wonder he works so well as a villain.
6 Moneybags - Spyro 3: Year Of The Dragon
This gluttonous bear debuts in the second Spyro game. He regularly charges a toll to open certain pathways or teach the dragon the moves needed to bypass obstacles. This forces players to collect the countless gems scattered throughout the realms. Moneybags makes an irritating roadblock, but he doesn't directly aid the villains.
That changes in the third game, where the "duplicitous ursine" is employed by the evil Sorceress. He's the jailer for the realms' other heroes--Sheila, Sgt. Byrd, Bentley, and Agent 9--and refuses to release them without a bribe. This takes all the annoyance of his extortionist ways and uses it to serve the enemy. At least the developers let you smack the stuffing (and gems) out of this bear in the endgame. It must be their way of apologizing.
5 Micah Bell - Red Dead Redemption 2
Micah is the exact type of classmate or coworker people can't stand. He knows just what to say to get in cozy with the boss while putting in as little effort as possible. This puts him in a higher position than those with actual integrity. When Arthur calls him out on it, he makes it out like he's the problem and throws him under the bus. That would be bad enough, but his underhanded actions have disastrous consequences.
Much of Red Dead Redemption 2's tragic events can be traced back to Micah. Kissing up to Dutch sends the gang leader further and further down his path of moral decay. He often encourages the boss's reckless plans, which distances Arthur and more honest members from the father figure they once knew. The nail in the coffin comes when Micah turns informer for the Pinkertons; he brings the lawmen right to the gang's doorstep. This outlaw is a rat in more ways than one.
4 Master Xehanort - The Kingdom Hearts Series
The man responsible for all the conflict thus far in the Kingdom Hearts series, Xehanort has brought untold misery to the various worlds and characters through his backstabbing. He resolves to remake the universe in his own design through a catastrophic Keyblade War, and he doesn't let anyone stop him. His best friend Eraqus tries to talk him out of it, but Xehanort scars his old buddy without a hint of remorse. He then tricks Eraqus's apprentice, Terra, into killing his master and turning to darkness. For the cherry on top, he possesses Terra's body and uses him as a vessel for future schemes.
Those schemes manifest in other entries. Xehanort uses his new body to usurp the position of scientist Ansem the Wise, stealing his research and unleashing a new wave of dark creatures on the world. No matter how many times the heroes think they've thwarted his evil, the clever Keyblade master hoodwinks them all. He plans for every contingency, and that's what's so frustrating about him. It's hard to beat someone smarter than you. The Kingdom Hearts characters learn that the hard way many times over.
3 Harry Flynn - Uncharted 2: Among Thieves
Nate should have known from the start: someone this slimy couldn't have been on the straight and narrow. Flynn is a thorn in players' sides for most of the second Uncharted adventure. After roping everyone's favorite treasure hunter into robbing a high-security museum, the greedy guy leaves him to rot in jail for three months. He spends the rest of the game licking the boots of main villain Lazarević, doing nothing to help yet basking in every victory over the heroes.
That gloating obviously means Flynn is easy to dislike. He always comes equipped with a smart remark, and he's more than happy to trade verbal blows with Nate. He knows the hero (and players) see him as an underhanded leech. He might as well have fun living up to that role; gamers have fun hating him as a result.
2 Neyla - Sly 2: Band Of Thieves
Another thieving franchise sees a supposed ally betraying the characters in the second entry. The difference is that Neyla doesn't stop there. This Interpol officer initially seems to see the greater good, helping Sly Cooper and his crew steal the malignant Clockwerk parts from the Klaww Gang. Sadly, she sets them up and throws them in jail. She also frames her partner--honest cop Carmelita Fox--for good measure.
These underhanded acts promote Neyla to captain, granting her the resources to acquire military weapons and mercenaries. She uses these to aid in her activities as a secret member of the Klaww Gang, only to eventually kill their leader and use the Clockwerk parts for her own destructive ends. There's not a single faction that Neyla doesn't double-cross.
Once Sly and company catch on, though, it feels good whenever they throw a monkey wrench in her plans. She comes in at the most inopportune times, but the Cooper Gang always outplays her through sheer ingenuity. These failures shatter her calm, condescending demeanor and make her steadily more desperate. Each one feels like a little slice of payback, one which gets sweeter every time.
1 Captain Qwark - The Ratchet & Clank Series
The folks at Insomniac seem to have a thing for money-grubbing oafs in their mascot platformers. Qwark has a sterling reputation as a galactic savior, and he's milked that reputation through merchandising and franchise deals. Such greed soon gets the better of him.
The superhero is not only a sham but a sellout as well. Ratchet & Clank seek his help to stop Chairman Drek and his planetary destruction scheme, but Qwark has already signed a contract with the malicious businessman. After this ends in disgrace, the former icon continues concocting harebrained plots to regain the spotlight. These efforts only get more and more pathetic. To be fair, Qwark later sees the error of his ways and goes straight, but his flamboyant enthusiasm often does more harm than good. Fans have a love/hate relationship with the green buffoon which extends across the whole series.