Regarding this point in Episode 3, am I the only one who found it excessively (and oddly) cruel for Obi-Wan to leave his student, his friend, his “brother” on the banks of a lava river to suffer and die slowly and painfully?! Finish him off, at the very least to put him out of his misery! If you ask me, whiny bitch as he was, Anakin/Vader was well justified in being an evil prick after that.
I guess… I’m not so sure killing Anakin would have actually accomplished anything useful. Luke and Leia would probably have received formal Jedi training but I’m sure somewhere in the universe, there’s another powerful bad guy who wouldn’t mind being an apprentice to a Sith.
In the novelization, there’s a line like (paraphrasing) “Obi Wan knew it would be merciful to kill Anakin quickly instead of leaving him to an agonizing death. After thinking about what had happened to the Jedi order, he did not feel very merciful.”