I understand people want to be positive about this show, and it has some decent moments, but I don't understand the praise it's getting.
Obi-Wan purposefully allowing Vader to live makes him directly responsible for any future atrocities. On Mustaphar, I understand why he didn't kill him. For this round, he's absolutely sure there's nothing of his friend left and the dialogue reflects as such. And yet, he walks away knowing that this will cause pain and suffering for millions, if not billions. We know Obi-Wan has no trouble killing for the greater good (Grievous, among others), so this makes no sense. Even if you enjoy everything else about the show, this is a troubling precedent.
Wouldve been much more interesting finish to see Obi-Wan slash him up to the point he thinks he has killed him. That way he has done what he thinks is the best for the greater good, but obviously Vader lives unknowing to Ben.