I find it strange people are so down on Luke. He's the best part of the movie IMO.
Seems like people are super hung up on the idea he'd try to kill a sleeping child and that the very idea is super out of character for Luke. And sure, maybe if you want to frame things like that you can convince yourself this is true... but it's not true. Anybody can be capable of anything if pushed into the right circumstances.
Let's imagine what happened that night.
Luke has been training Ben Solo and a bunch of other students for a while. But he's noticed Ben is a bit too aggressive than normal. He's vicious in training. He has explosive bouts of anger. He often goes too far when practicing forms and destroys things, like how Rey destroyed that one stone outcropping on the island by accident. Maybe Luke is also aware of some kind of contact Snoke has had with Ben in the past.
So he decides to touch his mind while he's sleeping with the force and see what Ben's true feelings are and if he's intentionally creeping towards the dark side. So Luke comes to Ben when he's sleeping and mind melds or some shit. When he does this, he senses the overwhelming evil Ben is capable of. it's terrifying. He can see that not only is Kylo Ren capable of mass murder, but also the murder of those around him. Not only is he capable of this, but he WANTS to do it. Out of pure horror and instinct, he feels that this darkness has to be stopped before it can do any of those things.
Then looks down at his hand and see he's drawn and activated his lightsabre. He's even more horrified at what was about to do than even what he saw in Ben's mind. So he turns off the lightsabre and leaves, resolving to find a way to save Ben from himself.
To me, this entire sequence seems COMPLETELY believable and within Luke's character. He's always been quick to fight when called for, but reflective of the implications of what he does. Honestly, this is definitively Luke.
The hiccup in this scene comes when Ben wakes up and sees Luke looking down in horror on his activated lightsabre. There's not really any other way to interpret that other than Luke is about to kill him in his sleep so he reacts appropriately and developes a burning hatred for Luke, the master who betrayed him.
And what can Luke do to convince him otherwise? He really did have a moment of reactionary weakness where he did want to kill Ben. "Oops, sorry, I was gonna kill you but I changed my mind." How can he explain this to Ben, or to Leia, or to Han? How can he even justify this to himself?
Luke is a good guy. He's an astonishingly good guy. And he had a very brief but understandable moment where he felt like killing Kylo Ren was the best thing to do. And he's deeply ashamed of it. Now he sees HIMSELF as the monster. Of course he does. He's a good guy. Good guys dont kill kids. So he must be a pretty bad fucking guy. The universe is better off without him.
So that's why he lives in exile. That's why he does everything he does in the movie.
And it's awesome.
It's really weird to see the same people complaining about Luke as the same who say this movie played it safe or took no risks. Yeah, apparently having Luke briefly consider killing a kid and becoming a bitter old man due to it is both playing it safe and completely out of character for OT Luke.
Also I'd like to applaud this terrific post as laying out exactly why Luke was so great in this movie and why it's such a triumph overall
I would have loved to have seen Luke wreck shit but in an era of easy and constant fanservice I'm glad they did something different that served story and character in a far more interesting way. ---