There have been many fantastic villains in video game history, from iconic figures like Bowser to truly reprehensible individuals like Micah Bell. However, some of the worst evildoers aren't born that way. Plenty of them start out on the side of good. Throughout the game or series, though, they change their allegiance.
Many turn because they've become corrupted in some way, whereas others finally show their true colors after deceiving the protagonist. Regardless of how they get there, they make for interesting antagonists because of the player's existing connection to them. Yet, not every hero-turned-villain is the same. These are the ones that rise above the rest.
10 Wheatley - Portal 2
In the original Portal, Chell only had the voice of the manipulative GlaDOS to accompany her. The sequel, though, adds a few new characters, including Wheatley. This AI takes the form of a small core early in the game and assists Chell in getting past all of GlaDOS's tests and traps. He then helps end her reign as the operator of the Aperture Science Enrichment Center.
But this is where the problems begin, as the hilarious companion takes her place and immediately becomes drunk with power. As a result, the protagonist spends the rest of the game trying to take down the new rogue AI.
9 Solas - Dragon Age: Inquisition
Throughout most of Dragon Age: Inquisition, Solas serves as a seemingly loyal ally to the protagonist. Not only does he accompany the Inquisitor on their adventures, but he's also a potential romantic option for the hero. However, in the epilogue of the game, it's revealed that Solas is actually the Dread Wolf and indirectly caused plenty of the problems that the heroes ended up solving. His villainous nature is then confirmed in the Trespasser DLC, where he speaks of his evil plans for the world.
It can be argued that the elf was never a hero in the first place, as he was hiding his real identity. Yet, he still helped put an end to Corypheus and save the world.
8 Alex Mercer - The Prototype Series
Prototype isn't a series known for its deep storytelling. However, it's interesting what the games do with Alex Mercer. In the original title, he is the main protagonist, but he's not the perfect hero as his actions can be cruel. For example, he does release a deadly virus on Manhattan. Yet, he redeems himself by saving the city from getting destroyed in a nuclear blast.
During the sequel, though, he goes from anti-hero to straight-up villain. This transformation is a result of his newfound hatred of the human race. To punish them all, he causes a fresh outbreak.
7 Sarah Kerrigan - The Starcraft Series
Sarah Kerrigan's turn to the dark side in Starcraft is more tragic than most, because it's not really her fault. During a mission for the Sons of Korhal, she finds herself in a tricky situation as the Zerg advance on her position. The leader of the group, Arcturus Mengsk, decides not to help her and gives his fleet other orders.
As a result, she's captured by the evil swarm, who transform her into the dangerous Queen of Blades. With her new powers, she sets out for revenge on the one who wronged her. However, in the meantime, she and the rest of the Zerg take many lives.
6 Arthas Menethil - The Warcraft Series
While Arthas Menethil is never the friendliest individual, his goals at the start of Warcraft III are noble. He wants to protect his people from danger, including the Plague of Undeath. However, it's this same cause that leads to his fall from grace. The Prince becomes so desperate to save his subjects that he resorts to questionable methods. He even takes the cursed blade known as Forstmourne, which truly converts him to the dark side.
The sword helps the Lich King take Arthas's soul, and the once honorable Prince joins the evil Scourge army. Not long later, he merges with the Lich King to become one of the strongest and most evil beings in Azeroth. His is one of the more tragic stories in the series.
5 Liu Kang - The Mortal Kombat Series
As Mortal Kombat is a series about a group of fighters ruthlessly brutalizing each other, it's hard to consider any of them heroes. Yet, Liu Kang is one of the few to come off as a noble person – albeit one that still drops arcade machines on their opponents.
He isn't able to remain that way through the entire series, though. After Raiden inadvertently kills the fighter, he is brought back as an undead revenant and serves the cruel Quan Chi. In this form, he becomes the joint leader of Netherrealm alongside Kitana. Thankfully for Earthrealm, some time-travel antics bring Liu Kang back to the side of good in Mortal Kombat 11.
4 Superman - The Injustice Series
The compelling stories of the Injustice titles are the main reason why they're considered among the best superhero games of the 2010s. In the first, The Joker tricks Superman into killing a pregnant Lois Lane and destroying Metropolis in the process.
This awful situation creates a universe in which Superman becomes an extremely dangerous tyrant, intending to kill all he deems immoral. He rules the world with an iron fist, and even his old superhero friends are forced to do his bidding. It's a version of the Son of Krypton very different from the one usually shown in other media. He returns in the sequel, once again causing problems for Batman and company.
3 Gabriel Belmont - The Castlevania Series
Castlevania: Lords Of Shadow follows the adventures of Gabriel Belmont as he hunts down the titular antagonists. Unfortunately, though, the quest ends up being both physically and mentally tasking. Upon completion, he isn't even able to revive his wife like he'd been led to believe.
The challenges don't stop there for the hero, as he then has to destroy The Forgotten One. To do so, however, he needs to get rid of the last remaining bit of humanity he has left and become a vampire. All of these events contribute to Gabriel's eventual transformation into the infamous vampire known as Dracula. Under the new moniker, he becomes a ruthless killer.
2 Kain - The Legacy Of Kain Series
The main character of the Legacy of Kain series begins the story as a nobleman, but it isn't long before he's murdered by a group of assassins. Kain gets another chance at life, albeit as a vampire instead of a human. At this point, he becomes a truly powerful anti-hero with intent on getting payback. Yet, his adventure becomes more complex than a simple revenge plot.
Kain slowly learns to accept his new life as a ruthless vampire. By the events of Soul Reaver, he's less of an anti-hero and more of a complicated villain. This puts him in direct conflict with the new protagonist Raziel.
1 Big Boss - The Metal Gear Series
The story of Big Boss's descent into madness is actually told in reverse. During the first two Metal Gear games, he is a villain who aims to create a world of perpetual war in order to give soldiers a place in the world. Some of his adversaries (for example, The Patriots) are arguably worse. That being said, he is still not an honorable individual at this point of the story.
Years prior, though, he saved the world on several occasions. From stopping Volgin to destroying Peace Walker, his heroic exploits were legendary. Players can bear witness to them in some of the later entries in the series.