To put it mildly, Emperor Palpatine caused quite a stir when he returned in The Rise of Skywalker by means of a cloned body. However, Star Wars has a long history of clones being involved in major, galactic-shaping events. For instance, Palpatine also found a way to cheat death in Star Wars Legends’ Dark Empire comic series, and the Grand Army of the Republic in the prequels was made up of mostly clones. While the prequels made most clones seem like an ostensible force for good; that was not always the case.
Originally most clones were looked down upon. For much of Legends continuity, fans thought that clones were the villains in the ancient Clone Wars that Obi-Wan mentioned in A New Hope. Part of the reason for that was what happened in Timothy Zahn’s Heir to the Empire trilogy and its comic adaptations by Mike Baron, Olivier Vatine and Fred Blanchard. Uniting with Grand Admiral Thrawn, one Dark Jedi clone named Joruus C'baoth, caused a lot of trouble for Luke, Leia and the New Republic.
Joruus C’baoth was a clone of Jedi Master Jorus C’baoth, with the double vowel in his name denoting his status as a clone. Jorus was an odd Jedi even before being cloned. He was the leader of the Republic’s exploratory, extragalactic mission called Outbound Flight and was killed by Grand Admiral Thrawn somewhere in the Unknown Reigns. It was during preparation for that mission that Palpatine obtained a tissue sample from C’baoth and used it to create a clone of the Jedi Master using Spaarti cloning cylinders, which were known for producing mentally unstable clones.
Disappearing during the Original Trilogy, C’baoth reappeared on the planet of Wayland sometime after Palpatine’s death aboard the second Death Star. There, he killed Palpatine’s guardian at Mount Tantiss and took control of the deceased Emperor’s hidden storehouse of dark treasures and cloning technologies.
Shortly after that, Grand Admiral Thrawn discovered Mount Tantiss and wanted to use its cloning technologies in his war against the New Republic, but when he found out that C’baoth was a Jedi, Thrawn also wanted to use his battle mediation to his advantage. C’baoth tried to kill Thrawn with Force lightning, but Thrawn had taken precautions with a Force-deflective bubble. Promising the deranged clone access to Luke Skywalker to make an army of dark Jedi, the two entered into an uneasy alliance.
C’baoth was invaluable to Thrawn’s military campaign because of his battle skills, but C’baoth’s madness – combined with a habit of mind-controlling Thrawn’s troops -- eventually became too much to handle. So, Thrawn imprisoned him on Mount Tantiss where Luke and Mara Jade would later confront the evil clone.
When Luke and Mara arrived at the throne room on Mount Tantiss, they refused to turn to the dark side, so C’baoth revealed his secret weapon – a clone of Luke. C’baoth had made Luuke (note the double vowel) using tissue from Luke’s severed hand which had been cut off by Darth Vader on Bespin and later recovered by Imperial forces. After a fierce duel, Mara killed Luuke and also killed C’baoth -- who exploded in a blast of dark side energy -- ending the terror that the evil clone had caused. With help from Leia, Lando and Chewbacca, they set charges to destroy the mountain after they left so that Thrawn could not create any more troops for his army.
C’baoth and Luuke may have not made it into canon yet, but their existence in Legends set the precedent for powerful, Force-wielding clones in Star Wars. On the other hand, Palpatine rose from the dead like he did in Dark Empire, so maybe C’baoth, or someone similar, will eventually return to canon.