Here’s an idea I don’t think I’ve seen here before-

Someone on Youtube has added scenes from the ST to a vision Luke has as he looks within Kylo’s mind during the Rashomon flashback scenes, so that the audience can see the darkness within Kylo that horrified Luke enough for him ignite his lightsaber in reaction:

https://www.youtube.com/watch?v=Eg4fZlt197U

I think it works really well, and actually seeing what Luke sees (show, don’t tell) helps the audience understand why Luke considered striking a student.

You could use scenes from all three movies. I’d probably choose the some shots more focused on Kylo than on Sidious, but either way it also adds a layer of irony - played out this way it’s almost like Luke saw a dark future that he feared, but through his fear, he actually brought it to pass.