Luke went to the ends of the earth to save the second most evil man in the galaxy. Showing that much doubt is out of character.
You should reread Lord of the Rings. Your understanding is a bit hazy. The Force is not just power. The Ring is raw power.
I am saying, that he just could not control his emotions for seconds. In original trilogy he almost killed his father, too.
I understand that. I was talking about the movie, tho. I watched it when I was a little kid. Will rewatch it soon.
Ah, that makes a lot more sense. The Lord of the Rings movies subtly change some parts from the books which alter the meaning slightly. The ending isn't quite the same in the books, though the movies did make it quite cinematic.
Luke showing dark side tendencies was one of the strong parts about Luke's character in Return of the Jedi, but Luke doubting himself isn't consistent with that. His dark side tendencies were of anger, not fear.
Oh, I want to read books more, but it is way more dry, as people say, so I am holding.
Sure and thats actually good point, but in both cases, emotions won over him, so he lost control for short amount of time. And cases were also different, bacause Vader was already on the dark side and they were fighting. So, I think, from here comes his doubts.
Could not find subtitles, but as I heard, he said, that he sensed dark side (Here he tried to kill Kylo - because it was so strong, that he thought Snoke already turned him evil), but then that Darkness faded (Here he was ashamed).