The Jedi Knights were among the main heroes of Star Wars: The Clone Wars, but not all remained altruistic throughout the war; some fell under the corrupting influence of the dark side. The Clone War itself was ultimately a conspiracy. Both sides were controlled by the Dark Lord of the Sith, Darth Sidious, who sought to turn the Galactic Republic into the Galactic Empire and eradicate the Jedi. His plan succeeded and the tragedy of The Clone Wars series is the utter futility of the Jedi and clone troopers’ victories and sacrifices. Before the Republic fell, some Jedi began to see the extent of the Republic’s corruption and the Jedi Order’s flawed ways, leaving them vulnerable to the dark side.
As shown throughout the Skywalker Saga and non-movie material from both the canon Star Wars timeline and the Expanded Universe (aka Legends), the dark side of the Force is a seductive corruption of the Force’s natural balance. The brutality and seemingly-perpetual quality of the Clone Wars left numerous Jedi traumatized and frustrated, making them lose faith in the ways of the Jedi and turn to the dark side out of desperation.
By the time the Clone Wars broke out, the Jedi Order had fallen from the das of the High Republic. Jedi were taught from a young age to suppress their emotions and eschew attachments leaving many Jedi lonely and ill-equipped for the harsh realities of a full-scale war. For some, the dark side offered freedom from the restrictions of the Order along with the power to end the war sooner.
Count Dooku
During his time as a Jedi Master, Count Dooku became gradually frustrated with the Republic and Jedi Order’s corruption, which often went hand-in-hand. Having grown up during the final years of the High Republic era, Dooku likely saw the Jedi decay into their prequel-era disconnection with the beings they swore to protect. A decade before the Invasion of Naboo, Dooku formally left the Jedi Order and became the Sith Lord Darth Tyranus sometime after Darth Maul’s presumed death.
As a Sith Lord, Dooku founded the Separatist Alliance. The Separatist Crisis (and subsequently, the Clone Wars) was meant to divide the galaxy and allow the Republic to be turned into the Galactic Empire. Dooku was successful in his Separatist endeavors, but he never lived to see the rise of the Empire. Killed and supplanted by Darth Vader before the Clone Wars concluded, Dooku’s only legacy was that of a traitor and a scapegoat for the Empire.
Asajj Ventress
The Dathomirian Asajj Ventress lived a life of loss and tragedy. Although she was never an official member of the Jedi Order, she was raised and trained on Rattatak by the stranded Jedi Ky Narec. When Narec was killed by a pirate, Ventress flew into a rage, getting her first taste of the dark side’s power and brutally avenging her master. Ventress used the dark side to kill the warlords of Rattatak and conquered the planet herself. By the time the Clone Wars began, Ventress had joined the Sith as Dooku’s apprentice.
The kind person Asajj used to be resurfaced towards the end of the war (after Ventress left the Sith and the Separatists to become a bounty hunter). As shown in the novel Dark Disciple, Ventress once again embraced the Force to save Quinlan Vos (a Jedi who was also struggling with the dark side), sacrificing her life in the process.
General Pong Krell
General Pong Krell was one of the cruelest antagonists in The Clone Wars. It’s unknown when the Besalisk Jedi Master fell to the dark side, but his hatred of clones appears to be a factor that motivated his corruption. Krell refused to see and treat the Clone Troopers as living beings, and the clones under his command had higher mortality rates than any other Jedi. Krell’s prejudice likely opened him to the dark side, which gave him a premonition of the Jedi Order and Republic’s destruction.
Krell betrayed the Republic and sought to impress Dooku by cruelly toying with the clones of the 501st Legion, sending them on suicide missions and pitting them against the 212th Battalion in a calculated friendly-fire incident. Krell’s treachery led Captain Rex to lead a mutiny against him that ended with the fallen Jedi’s well-earned death.
Barriss Offee
Once a loyal and dogmatic padawan, the Mirialan padawan Barriss Offee began to see the Jedi as hypocrites as the Clone Wars dragged on. As Count Dooku had decades before, Barriss’s frustration with the Jedi eventually led to her being seduced by the dark side. Like Dooku, Barriss’ fall led her to become the true hypocrite. Barriss bombed the Jedi Temple on Coruscant, killing Clone Troopers, civilians, and Jedi (including one of her personal friends), and framing Ahsoka Tano (another friend of hers) as the perpetrator.
Though Barriss was eventually caught and revealed as the real traitor, her actions had far-reaching consequences. The experience led Ahsoka to leave the Jedi Order and Barriss’s criticisms convinced a Jedi Temple Guard to eventually betray the Jedi and become the Grand Inquisitor.
Quinlan Vos
The fall and redemption of Jedi Master Quinlan Vos highlights the corruption of the prequel-era Jedi Order. As shown in Dark Disciple, the Jedi Order was desperate to assassinate Count Dooku and discover the identity of his master. Vos was tasked with infiltrating the Separatists as a dark side user, and thus learn how to use the dark side of the Force from the former Sith Asajj Ventress. Vos and the Jedi Order as a whole learned the hard way that the dark side cannot simply be learned and abandoned so easily. The dark side’s corrupting and addictive influence, worsened by Dooku’s goading, proved too much for Vos to resist, and for a brief time, he truly was a Sith apprentice to Dooku. Asajj Ventress, at the cost of her life, managed to bring Quinlan Vos back from the dark side, but at the cost of Jedi and clone lives.
Anakin Skywalker
Anakin Skywalker’s tragic fall from grace was shown in detail in Star Wars: Episode III - Revenge of the Sith and heavily referenced in the series finale of Star Wars: The Clone Wars. Having already tasted the dark side in his massacre of Tusken Raiders and the execution of Count Dooku, Anakin was extremely susceptible to the dark side. To make matters worse, he was desperate to save his wife Padme from dying in childbirth, and the Jedi (with whom he was already losing trust) offered him nothing but platitudes. When forced to choose a side, he joined Darth Sidious, becoming the Sith Lord Darth Vader, and brought about the destruction of the Jedi, the rise of the Galactic Empire, and the end of the Clone Wars. But like every other Jedi to fall to the dark side, Anakin’s corruption robbed him of everything but himself and his power.