Removing the line, “the same way I will destroy you” makes it now seem like Vader expects to be killed. Like he’s saying, “You’re about to kill me but I beat you to it really.” And when Ben leaves him like that, he’s pissed to be shown mercy or possibly to not be killed again. Shows Vader’s guilt, to have been passed over rightfully being killed twice.
Good analysis Hal. Yeah when I watch the scene now even though I want Vader to die I also feel genuine pity for him as well. The last 3 episodes and especially the final fight made me want to salvage Kenobi.