9 Jedi Who Joined the Dark Side
Star Wars is a story of good vs. evil, and in order to maintain that divide, some Jedi have to take one for the team so to speak. Not that it sucks to have infinitely cooler powers and an awesome lightsaber, but I digress. Here are 9 Jedi who turned to the dark side (in canon).
Number 09. Ahsoka Tano
Although very brief, the Padawan of Anakin Skywalker was infected with the dark side. After being corrupted by the "Son" on Mortis, Ahsoka became filled with hate and a bloodlust for battle. She even fought her Master after declaring loyalty to the Son, and later died as a result of her delve into the dark side. Thankfully, Skywalker managed to revive her, returning Tano to the light side.
Number 08. Quinlan Vos
Assigned to assassinate CIS leader, Count Dooku, by the Jedi Council, Quinlan Vos attained the help of Asajj Ventress, who was formerly Dooku's dark side acolyte before being cast aside. The idea was to bring together both sides of the Force. However, Ventress turned the Jedi Master to the dark side, knowing it was a vital step in defeating the Count. Distancing himself even more with the Jedi Order, Vos became romantically involved with Asajj. After a failed attempt to kill Dooku, Quinlan was captured and subjected to the Sith's mind games. However, his life as a Separatist agent came to an end when he defeated Dooku in a duel, sparing his life just as a Jedi would. Because of this, he was accepted back into the Jedi Order.
Number 07. Pong Krell
Pong Krell served as a Jedi General during the Clone Wars, and was very effective in the role, even if his methods were "unconventional". But when the Besalisk foresaw the demise of both the Jedi Order and the Republic, with a new power replacing it, Krell chose to immerse himself in the dark side. However, his plans to serve Count Dooku were foiled by the 501st Legion, which ultimately led to his death at the hands of his former right-hand man, Dogma.
Number 06. Barriss Offee
Barriss Offee may have been extremely loyal to her Master, Luminara Unduli, and have struck up a close friendship with fellow Padawan Ahsoka Tano, but she grew disillusioned with the Jedi Order, believing that they were corrupt, arrogant and violent. Due to such, she teamed up with Letta Turmond, who shared her views, to make a statement against the Order. They both planned and executed a bombing in the Jedi Temple, which resulted in the false conviction of Ahsoka. However, the Togruta's Master discovered the truth and had Offee arrested after a brief duel. Offee was banished from the Order and imprisoned.
Number 05. The Grand Inquisitor
Once a Jedi Temple Guard after rising through the ranks of the Jedi Order, the future Grand Inquisitor lost faith in the Jedi Order following the events between Offee and Tano. As a result, he fell susceptible to the dark side, and ultimately joined it. Afterwards, he came into the service of the Galactic Empire, tasked with hunting down and killing any Order 66 survivors. One Jedi he led to her death was Luminara Unduli. After many years in the service of the Empire, the Grand Inquisitor willingly fell to his death after a duel with Kanan Jarrus and his Padawan, Ezra Bridger.
Number 04. Asajj Ventress
After a tough upbringing, Asajj Ventress' potential in the Force was discovered by Jedi Knight Ky Narec. After ten years of training, Ventress watched her Master die at the hands of Rattatak pirates and warlords. Left without guidance and only an introductory training of the power of the Force, Ventress embraced the dark side. When Count Dooku found her, she fell under his guidance and tutelage as an apprentice and aspiring Dark Lord. Throughout the Clone Wars, she loyally served the CIS, causing many problems for the Jedi Order. However, after she was betrayed by Dooku and his Master, she planned to exact revenge. Her life was cut short when she sacrificed herself to save her lover, Quinlan Vos, absorbing Dooku's Force lightning. But Vos honoured her sacrifice and rejoined the Jedi Order.
Number 03. Kylo Ren
As a Jedi under the training of Luke Skywalker, Ben Solo's obsession with his grandfather, Darth Vader, the feeling of abandonment and the influence of Snoke all factored in his journey to the dark side. After destroying his fellow students and becoming the leader of the Knights of Ren, Ben's transformation was complete. In the ranks of the First Order, the "Jedi Killer", renamed Kylo Ren, was tasked with killing the final Jedi, Luke Skywalker. His story may not yet be complete but redemption seems unlikely for Ren.
Number 02. Count Dooku
As a Jedi Master, Dooku became disillusioned with the corruption in both the Jedi and the Galactic Republic. After defection, Dooku turned to the dark side, where he became Darth Tyranus and served as the apprentice of Darth Sidious. He helped engineer the Clone Wars, oversaw the creation of the Galactic Republic's clone army, trained many dark acolytes, and helped orchestrate the Death Star. Unfortunately, Dooku's loyalty wasn't repaid by his Master, who saw a younger and more powerful replacement.
Number 01. Anakin Skywalker
He was by far the most significant Jedi to have turned to the dark side due to the horrendous implications on the galaxy his defection caused. Once a very promising Jedi, who was the Chosen One, Anakin Skywalker was plagued by emotions linked to the dark side. Following his mother's death, Skywalker feared he would also lose his wife. Desperate, the Jedi joined the dark side as Darth Sidious' apprentice. Once Padmé Amidala passed away, the newly named Darth Vader fully embraced the dark side of the Force. After serving the Galactic Empire for decades, he was restored back to the light by his son, Luke Skywalker. Before his death, Anakin fulfilled the Chosen One prophecy by destroying his former Master.
So there are 9 Jedi who turned to the dark side. Are there any more that I missed? Let me know in the comments below.