Merely by virtue of being strong, Obi-Wan kept pushing away the man he always looked to as a brother, losing him in the process. In the end, Obi-Wan finally gave up, giving Anakin what he always wanted by allowing him to defeat his former master — though not in the way Vader had always envisioned.
Anakin Skywalker and Obi-Wan Kenobi have a unique relationship in Star Wars: Attack of the Clones. The master and Padawan have profound mutual respect and admiration but are not afraid to question each other in times of conflict or uncertainty.
Obi-wan always loved Anakin. He tried to save Anakin even after Anakin massacred the younglings. Darth Vader being Anakin Skywalker was a retcon, but it worked brilliantly. Obi-wan shows no hatred or love toward Vader on the Death Star, but there is anger and frustration.
David Porter provides some great philosophical context to why Obi-Wan would not regret leaving Anakin alive, as it was obviously “the will of the Force” that Obi-Wan be unable to finish him off, and “the will of the Force” that Anakin live on to kill Sidious himself in the future.
No, but… it's complicated? Thing is, he never really felt like there was anything to forgive Anakin for. But he definitely never forgave Darth Vader. When Anakin fell to the dark side, Obi Wan took it as his own failure.
What If Obi Wan Kenobi Was With Anakin Skywalker During Revenge of the Sith
Why did Obi-Wan spare Anakin again?
There was no way for Obi-Wan to ensure that Anakin would become a Force Ghost or that he wouldn't become a malevolent Sith spirit. Given Anakin's natural gifts and his fated rise as the "Chosen One," Obi-Wan knew that solving the problem of Darth Vader wouldn't be as simple as just killing him.
So, at that moment on Mustafar, Obi-Wan should have finished Anakin, but he didn't have the courage to do it because ironically he had an attachment to Anakin. He couldn't even do what would be the best solution (take Anakin with him and try to bring him to the Light) or what the Order dictated (destroy the Sith).
Secondly, based on their last encounter on Mustafar, Anakin was obviously too far gone to the Dark side as he had just gone on a killing rampage in the Jedi temple. Obi-Wan thought that he's far beyond redemption; in hindsight, not really understanding what drove Anakin to the Sith didn't help the situation.
Of course, Obi-Wan didn't finish Anakin off ten years ago on Mustafar because he didn't want to be the one to strike the killing blow on a man that he loved like a brother.
This fell in line with various fan theories and non-canon novelizations that suggested Obi-Wan and Padmé had an affair sometime during the Clone Wars. In the Star Wars prequel movies, Obi-Wan often has a duty to protect Padmé, but there was never any sense of romantic feelings.
The Obi-Wan Kenobi is next in the Star Wars timeline, taking place nine years exactly ten years after Obi-Wan left his former apprentice for dead on the lava fields of Mustafar. This means Darth Vader is 32 in Obi-Wan Kenobi (his master, in contrast, is 48).
Anakin Skywalker was the most unappreciated Jedi in history, and had more members of the Order embraced him like Obi-Wan, Ahsoka and Plo Koon, he could have led the Jedi into a new golden age, rather than spearheaded their utter destruction.
Though Obi-Wan was often an important ally for Anakin, the young Jedi could never see past his envy, even going far enough to allow himself to believe that his master was having an affair with his wife. In the end, Anakin's own jealousy was his undoing and the reason that he would never surpass his master.
Palpatine may still have eventually traded Dooku in for a newer apprentice, but nothing would have hindered his rise to power. Had Qui-Gon trained Anakin and kept him far from Palpatine, Anakin might have eventually died in the Clone Wars and been completely unable to fulfill any Chosen One prophecies.
As the heat began to consume Anakin, a grief-stricken Obi-Wan turned away, unable to watch his former Padawan and friend die. But Anakin lived. Rescued by Darth Sidious, he was encased in black armor and became known as Darth Vader, the Empire's brutal enforcer.
The scene explains Obi-Wan's explanation to Luke that Darth Vader murdered Anakin Skywalker, because in a way, he did. The dark side of the Force is all-consuming. Once someone starts down the path to the dark side, it can be difficult to return to the light.
He meant that he "killed" that part of him. Anakin as in the jedi, the compassionate, good person he was is nowhere to be found after he turned to the dark side.
Vader responded “I am not your failure, Obi-Wan. You didn't kill Anakin Skywalker. I did.” This allows Obi-Wan to finally accept that Anakin is truly gone and that there was nothing he could have realistically done to save him.
The base assumption of why Obi-Wan doesn't remember R2-D2 -- in light of the prequels -- is that Obi-Wan is feigning ignorance in A New Hope to downplay the importance of the droid's arrival.
Kenobi bested Anakin, severing his limbs, and leaving him to die, burning on the shores of a lava river. Darth Sidious recovered Anakin's broken body and returned with him to Coruscant. Medical droids rebuilt Anakin with cybernetic parts, encasing him in dark armor to complete his transformation into Darth Vader.
