Vader's reaction was out of his mouth before he had time to consider his words. "I shall endeavor to teach this younger one to not be such a coward." Because both moves were in Vader's mind, the mark of cowardness.

He lifted his hand back to Kylo's face, his forefinger under the boy's chin, as his thumb traced over his cheek. The touch was light. He knew all too well the feelings of having to struggle under teachers and masters who feared you. Windu, he thought, would have done the same thing, had he been gifted with Foresight and the future not cloaked by Palpatine's efforts.

"I'm sure you were a brilliant student."