Here are all the Jedi who had survived Order 66, and who were still at large in the galaxy at the time of Star Wars: The Bad Batch. Emperor Palpatine envisioned the Clone Wars as the ultimate Jedi Trap, a no-win scenario where the Jedi lost simply by taking part. The Clone Wars were not epic, but in fact they were tragic. "Wars do not make one great," Master Yoda told Luke Skywalker in The Empire Strikes Back, and he was probably recounting a lesson he had learned when he reflected back on the Clone Wars.
There is a sense in which the Clone Wars were too successful. When the Clone Wars began, they tipped the galaxy toward the dark side, and the Jedi lost their ability to perceive the will of the Force. Over the course of the conflict, countless Jedi lost faith in their cause and in the wisdom of the Jedi Council, who were unable to see through the shroud of the dark side. The Jedi had more defectors during the Clone Wars than it did during the last thousand years, and after Order 66 - when the remaining loyal Jedi were slaughtered by Clone Troopers under Palpatine's control - these scattered former Jedi proved difficult to track down. The Jedi Purge began with Order 66, but Darth Vader would continue it for years.
Here are all the known Jedi and former Jedi to have survived Order 66, in rank order, and to still be alive at the time of Star Wars: The Bad Batch. It is quite possible some of their stories will interact with the adventures of Clone Force 99.
Master Yoda
The Grand Master of the Jedi, Yoda survived Order 66 because of his good relations with the Wookiees. As seen in Star Wars: Episode III - Revenge of the Sith, Yoda returned to Coruscant, and was one of the few Jedi to figure out how completely they had been deceived and manipulated. He confronted Palpatine himself, and was shaken to realize the Sith Lord was simply too powerful for him to defeat. And so Yoda exiled himself to the swamps of Dagobah, resolving to wait until the next generation came of age - the Skywalker twins who he believed to be the hope of the galaxy. He used the powerful Force Vergence at Dagobah to conceal himself from the Sith, biding his time but still providing long-distance training to any who stumbled into ancient Jedi Temples, as seen in Star Wars Rebels.
Obi-Wan Kenobi
Obi-Wan Kenobi was one of the few members of the Council to survive Order 66; while Yoda fought Palpatine on Coruscant, Obi-Wan was sent to hunt down Anakin Skywalker for his betrayal. Although Obi-Wan defeated Anakin on Mustafar, he chose not to kill him, with the Emperor recovering his fallen apprentice. Obi-Wan sent out a message to all Jedi, warning them to hide in the shadows, and then exiled himself to Tatooine to watch over Anakin's son Luke as he grew up.
Jocasta Nu
Jocasta Nu was the Jedi Archivist during the prequel era, and she and her assistant Gar escaped with many of the Jedi's most important records. She secreted these away on an unknown world, but unfortunately made the mistake of returning to Coruscant in order to try and rescue more secrets of the Jedi she did not want the Sith to possess. She was captured by Darth Vader, who killed her; the cache was discovered decades later by Luke Skywalker as he worked to rebuild the Jedi Order.
Oppo Rancisis & Coleman Kjac
Oppo Rancisis was an aged Jedi Master who had sat on the Council since the High Republic Era, and he appears to have survived Order 66 as well. Both he and his fellow Council member Coleman Kjac were named on an Imperial list of survivors in Darth Vader #19, although they haven't been seen, meaning there's no idea what they did during the Dark Times. They were high on the Empire's list of targets, so their chances of survival through to the original trilogy era are slim.
Eeth Koth
Although Eeth Koth had served as a member of the Jedi Council in the prequel era, he stepped down from the Order in the last days of the Clone Wars. Koth abandoned his allegiance to the Jedi Order, hiding among the Church of the Galactic Enlightenment, but he was eventually found by Darth Vader and slain. His child was kidnapped by the Empire to become part of Project Harvester.
Quinlan Vos
Although Quinlan Vos was a Jedi Master, as seen in Star Wars: The Clone Wars he was unusually susceptible to the dark side of the Force, and he actually became apprentice to Count Dooku. Vos' love for Ventress redeemed him, and he resolved to abandon the Jedi Order. Little is known of Quinlan Vos' fate after Star Wars: Episode III - Revenge of the Sith, but Vos' name has been mentioned as an Order 66 survivor, with the Empire hunting him down.
Cere Junda
Introduced in Star Wars Jedi: Fallen Order, Cere Junda was a Jedi Knight who trained a number of Padawans during the prequel era - and somehow survived Order 66. She and her Padawan Trilla Suduri escaped their Clone Troopers, and even rescued a number of Jedi younglings. Unfortunately Junda was captured by the Empire, and forced to give them up. She subsequently escaped, suppressing her connection with the Force for fear of the dark side, and vanished into the criminal underworld for a time.
Kira Vantala
Little is known of Kira Vantala, a Jedi Knight who is introduced in George Mann's Dark Legends. One story, "The Orphanage," reveals the Inquisitors were frequently visiting the planet Gaaten in order to acquire Force-sensitive children, and their repeated visits drew the attention of Kira Vantala, who confronted Second Sister. The story - set at an unknown point during the Dark Times - actually sees her take on a Padawan of her own, a young orphan named Elish.
Naq Med
Naq Med is another enigmatic figure, apparently a Jedi Knight during the Clone Wars who began to doubt the wisdom of the Order, believing they were too involved in politics. Naq abandoned the Jedi, renouncing his vows, and he married and started a family. He believed the Empire's propaganda about the Jedi Rebellion, deeply regretting his past participation in the Order, and after an encounter with an Inquisitor he fled into the shadows. Naq Med settled on a remote, largely uninhabited planet called Pam'ba. He lived there until Kevin Shinick's novel Force Collector, which is set shortly before the events of Star Wars: The Force Awakens. Naq Med appears to be the longest-living Order 66 survivor.
Caleb Dume, aka Kanan
Caleb Dume, who came to call himself Kanan, considered himself the last Jedi Padawan to survive Order 66. The story of his survival is told in Greg Weisman's Kanan series, which reveals he was saved by his Master, Depa Billaba. He hid away in the galaxy's criminal underworld, moving from planet to planet, hunted by the Empire wherever he went. Kanan would ultimately find his way into the Rebel Alliance, remaining active until shortly before the events of the first Star Wars film.
Cal Kestis
Star of the Jedi: Fallen Order game, Cal Kestis was another Padawan who was saved by the heroism of his Master. He went into hiding on the junk world of Bracca, finding work by joining the Scavenger Guild as a successful rigger. Cal took Obi-Wan Kenobi's command to hide seriously, doing everything he could to avoid attracting the attention of the Empire until several years later.
Ferren Barr
A Padawan who survived Order 66, Ferren Barr fled to the aquatic planet Mon Cala, where he spent months attempting to discover how the Jedi Order had fallen so quickly - and even learned Anakin Skywalker was Darth Vader. Ferren Barr attempted to restart the Jedi Order on Mon Cala, but his teaching and methods were undermined by his anger, which left him vulnerable to the dark side. He was eventually discovered by the Emperor, and Darth Vader destroyed his pseudo-Jedi Order.
Ahsoka Tano
Ahsoka Tano had technically left the Jedi Order in Star Wars: The Clone Wars season 5, her confidence in the Council shaken when they blamed her for a bombing at the Jedi Temple. She returned to ally with the Jedi during the Siege of Mandalore, with Order 66 called almost immediately afterwards. As seen in Star Wars: The Clone Wars season 7, Ahsoka managed to help her friend Rex break free from Order 66, and the two escaped. According to E.K. Johston's novel Ahsoka, the former Padawan sank into the shadows of the galaxy, but over the course of the next year or so she realized she could not stand idly by. The opening scenes of the novel contrast markedly with Star Wars: The Clone Wars season 7, so it remains to be seen whether Lucasfilm will modify Ahsoka's story.
Other Surviving Jedi
Various lists have named other Jedi who survived Order 66, although little is known about them beyond their names. Darth Vader #19 named some Order 66 survivors, notably Selrahc Eluos and Ka-Moon-Coli; the first is an anagram of writer Charles Soule, while the second immortalizes artist Giuseppe Camuncoli in Star Wars. The mobile game Star Wars: Uprising revealed another three Jedi - Zubain Ankonori, Nuhj, Khandra, and Mususiel - had hidden themselves at an ancient Jedi shrine on Anoat with three others, although they would eventually be discovered by the Empire. Whether Star Wars: The Bad Batch will flesh out any survivors, or reveal more, remains to be seen.