Vader's defeat at the hands of Obi-Wan in the Obi-Wan Kenobi season finale actually mirrored Anakin's earlier mistake in their climactic duel on Mustafar. Throughout the Star Wars saga, Anakin's (and later Vader's) arrogance and impetuosity have perhaps been the character's two major flaws, putting him in constant peril. There is no greater example of this trait than the two duels, where his hubris ultimately spells his downfall. While the epic Obi-Wan Kenobi battle is full of callbacks to the protagonists' previous encounters, the repetition of one particular error proves that Vader is still constrained by Anakin's biggest weakness.
Midway through the fight, before Obi-Wan has fully rediscovered his connection with the Force, Vader successfully casts his old master into a rocky pit. Towering over him, before seemingly burying him alive, Vader seems to have finally proven his old hypothesis about the prominence of possessing the "high ground", subtly reiterating his belief that Obi-Wan has "underestimated [his] power" in the process. In once again believing his own hype, Vader demonstrates his failure to learn from the Mustafar error that cost him his limbs and turned him into more machine than man. In the process, Vader echoes his worst mistake – that he believes he can get away with anything, regardless of the situation or opponent.
Vader Hasn't Learned From Anakin's Mustafar Mistake
While there is considerable debate over exactly how Obi-Wan managed to beat Anakin in Revenge of the Sith, the improbability of his triumph actually highlights the central lesson of Anakin's Mustafar defeat – that it was as much about his own arrogance as it was about Obi-Wan's ability with a lightsaber. In forcing his attack too early, believing that he had his old master where he wanted him when really his own situation was equally perilous, Anakin gave Obi-Wan the opportunity to win the battle, when the two Jedi's skills suggest that he should have been able to triumph. Likewise, in Obi-Wan Kenobi, Vader lectures Obi-Wan before prematurely assuming he has the upper hand. In failing to press his now-genuine advantage as a result of his arrogance, he compounds his earlier mistake and once again reveals his fatal flaw.
By putting Vader at a clear advantage, Obi-Wan Kenobi reverses much of the Mustafar dynamic. However, the show doesn't offer an exact repeat of Anakin's original mistake. Instead, it changes the scenario to make a wider point about Anakin/Vader's character, making the scene much more than a highly anticipated rematch. Although Anakin and Vader are presented with two different situations, in both instances they are undone by an innate and inescapable arrogance, making both scenes more memorable and enhancing the character(s) in the process.
Obi-Wan Kenobi Finale Also Repeated An Obi-Wan Error
While Vader's arrogance clearly calls to mind Anakin's Mustafar mistake, the composition of the fight also highlights Obi-Wan's own problems. In both battles, Obi-Wan walks away from his former apprentice, unable to land the final killing blow, instead assuming that he's already done enough. As the rest of the Star Wars saga demonstrates, this is clearly not the case. Had Obi-Wan not let Vader live on two occasions, it's undeniable that the fate of the entire galaxy would have been very different, with untold lives potentially saved. While his mercy is a much more sympathetic trait than Vader's arrogance, the fact that Obi-Wan once again fails to finish the job only makes Vader's later crimes more tragic.
Interestingly, Vader also displays Obi-Wan's apparent unwillingness to land a definitive blow. Like his master did on Mustafar, he walks away when the fight is seemingly won, leaving Obi-Wan trapped underground, pinned by rocks when it would have been easy to end things then and there. The fact that this mirrors the end of their original duel not only highlights the cyclical nature of the pair's relationship, but perhaps indicates that Vader has not entirely forgotten his Jedi teachings. In any case, the various similarities and juxtapositions between the Revenge of the Sith and Obi-Wan Kenobi fights add greater depth and complexity to the two combatants than ever.