Vader doesn't regret falling to the Dark Side (Anakin does). He regrets being defeated by Obi-Wan. That's why, when he sees that Obi-Wan is full of guilt, and no longer wants to kill him, he "comforts" him by saying that he's not his failure.
For years, Vader hated Obi-Wan, having been struck down by his mentor and left for dead while also believing the Jedi had worked to turn his true love Padmé against him. However, there's another, far darker reason Vader hated Obi-Wan so obsessively.
But Vader refuses to accept this apology, shouting "I am not your failure Obi-Wan. You did not kill Anakin Skywalker. I did, the same way I will destroy you!"
After his redemption, after bringing back balance to the force, after the return of the Jedi, Anakin would have definitely held a bit of remorse, not to forget, it was Obi-wan who taught Anakin how to become a force ghost, to stray oneself from the cosmic force and assume identity with the living force.
At the time, it's likely Obi-Wan smiled because he was about to become one with the Force, and he was fine with that after seeing Luke, their last hope, make his great escape.
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.
Anakin does not have even the slightest bit of remorse. By the end, he feels nothing but anger. Although he feels regret for killing Padme, he still helps the evil Emperor. The film ends with Anakins standing side by side with the man on whose behalf he has committed all his crimes.
The short answer is yes, without a doubt, Vader regretted becoming a cybernetic monstrosity. First, there's the constant pain and discomfort from his suit. Worse, however, is the psychological pain. Vader destroyed everything he had ever known for a chance to save Padme.
The canonical comic Star Wars: Darth Vader #7 confirms the younglings' deaths caused Anakin grief, self-loathing, hatred and pain, fueling his descent even further into the dark side.
In a way, Obi-Wan and Anakin were like orphaned brothers, both of them left parentless after the death of Qui-Gon Jinn. As he turned to the Dark Side and became Darth Vader, Anakin came to hate Obi-Wan, but never stopped respecting him.
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.
This could be interpreted as Obi-Wan showing either pity or mercy for his old friend. Despite everything they have been through, the Obi-Wan Kenobi show has firmly established that the Jedi still deeply cares for his former Padawan and remembers him as the great ally he's had for many years.
learn how Vader felt upon striking down Kenobi. from Yoda, rather than feeling relief. or vindication at finally destroying his old master, Vader, or rather Anakin, was instead. overwhelmed with utter loneliness and sorrow, having killed one of his last. remaining links to his former life.
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.
However, when it comes to who Darth Vader hates more than anyone in the Star Wars galaxy, himself and Obi-Wan Kenobi don't hold a candle to the true point of Darth Vader's hatred, Emperor Palpatine.
The reborn Sith Lord was aware that the Jedi believed Skywalker to be their prophesied Chosen One, and that Vader still considered himself as such despite his fall to the dark side.
In essence, the more one holds hatred for someone, the more power that person has over them. By hating Palpatine more than anything, Darth Vader is admitting that Palpatine is the true source of his power, and is therefore far too important for Vader to kill (even on a subconscious level).
At some point after his transformation into the armored Darth Vader, Amidala's husband, the fallen Jedi Knight Anakin Skywalker came to visit the mausoleum, stricken by grief and remorse for his part in her death.
tragically, he was not able to resurrect Padme. because she refused to go with him. due to his inability to let go, telling him she didn't know him anymore, jumping away from him to her death.
Darth Vader hates Obi-Wan, not because he blames him for his fall to the Dark Side, but because he turned Padmé against him and destroyed his body. The line from Obi-Wan Kenobi, "I am what you made me" isn't a reference to Vader's fall to the dark side.
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.
By the time Star Wars: A New Hope occurred, Darth Vader finally considered himself superior to Obi-Wan, prompting him to declare that he was now “the master” between the two of them. In addition, Darth Vader's line in Star Wars: A New Hope suggests that he and Obi-Wan will duel again in Obi-Wan Kenobi.
