Michael F. Assbender
Banned
I took it to be Kylo trying to drive Rey to submission, and if she did not give up, he'd cripple her if needed. That's why he waited until he had her pinned to even say anything. (Also, Kylo Ren is not a Sith, but that's also nitpicking. )
I agree with this. Here's the entire fight (the file was huge, so I broke it into three parts--only cutting out part of Poe's X-Wing badassery--then compressed them so I didn't kill anyone's browser. Please forgive the artifacts):
Then the planet gets blowed up real good (these last two I shrunk because they were still huge):
And the final bit:
Notice she's on her back foot the entire time, only showing any skill after Ren mentions the Force, leading Rey to close her eyes and focus (which is exactly what Maz had directed her to do in the bar). Ren is being cocky.
He's too sure of himself, just as he was with Finn:
He even knocked Finn down and just walked away instead of finishing him off.
Finn gets up and:
Ren continues to fuck with him, spinning his saber like a cocky bastard, then torturing Finn with the short tip.
Finn desperately pushes him away and swings, hitting Ren with a lucky strike, and Ren stops fucking around:
Look at that--when Ren gets real, Finn is instantly disarmed and left comatose (and possibly paralyzed, because damn, look at what he did to Finn's back).
He's just toying with them. Hell, he likely would've ended Rey long before awakening the Force within her if not for something very important Snoke said:
You don't disobey that. You try to tire her out; get her to submit; maybe convince her to join you in embracing the Dark Side of the Force.
His ego (not a lack of skill) was nearly his undoing against Finn before he decided to end the fight, and a combination of ego plus Snoke prevented any such beatdown of Rey.