RE: Why doesn’t Ben kill a defeated Vader?
Jedi Knights are honourable and chivalrous. Killing an opponent in a duel is one thing, but killing a vanquished fallen opponent is something entirely different. That is an execution.
We already see that when Anakin ‘executes’ a defeated Count Dooku. It is a wholly evil thing, and not the Jedi way.
So leaving Vader alive to murder millions of people is honourable and chivalrous? The situation with Dooku is not comparable, because Anakin had the option of letting Dooku stand trial. Obi-Wan on the other hand has to choose between two evils, where letting Vader live is clearly the worse option. Also, Yoda in ROTS sends Obi-Wan to kill Anakin, and Obi-Wan tells Luke, that if he will not kill Vader, the Emperor has already won.
Leaving Vader alive results in Palpatine’s defeat and the fall of the Empire (at least until Palapatine returned “somehow” lol).
“Many that live deserve death. And some that die deserve life. Can you give it to them? Then do not be too eager to deal out death in judgement. For even the very wise cannot see all ends.” to bring a bit of Tolkien into the Star Wars chat!
Anyway, I stand by my point that a Jedi executing a fallen foe would be completely out of character with the compassion and chivalry that is their code.