Tangible God
Lets all love Lain
*groans* My head aches from trying to keep track of this.
Again, Obi-Wan knew the danger Vader presented to the galaxy, and he knew that, if Anakin could not be redeemed, the he must be destroyed. Both Yoda, and the Jedi mandate told him that.
He did try, I'll give him that. It didn't work. So now, it would be his duty to the Republic, the Jedi, and Anakin himself, to destroy Vader. Which he didn't. I'll admit that, not having been through the life of Obi-Wan Kenobi, I could not kill someone that close to me. But I do not possess the gift of the Force, or the experience, wisdom, and logical behaviour of Kenobi. HE does. He should have had the foresight and common sense to see that leaving Vader there, as wounded as he was, was not a sure guarantee of his death, especially considering Vader's obvious, and furious rage, which would not be a hindrance in his survival.
THAT was his mistake. Assuming that Vader would die there, without overseeing it done. Yes, we understand WHY he made that mistake, but it was still a mistake all the same.
In the long run, his actions saved the galaxy. But who's to say the galaxy wouldn't have been saved sooner, had Vader not been a factor?