After watching "Star Wars: The Force Awakens," I wrote about looking forward to seeing Kylo Ren grow as a villain. In that piece, I described Kylo as a petulant brat, but there were also other layers to this antagonist who's willing to kill his own father to prove a point to himself.
Like I hoped it would, "Star Wars: The Last Jedi" gives us more details about what drove Ben Solo's transformation into Kylo Ren, and, thank goodness, it's not clean-cut. You see a history of grown-ups he looks up to consistently letting him down. There are his parents, to start with, who send him away to train as a Jedi. Though we don't know how Kylo actually felt about that, we've often seen, in the Star Wars universe, that children are rarely happy about being sent away. There's his uncle Luke, also his Jedi master, who tries to kill him in his sleep! Luke, who thought he was preventing Kylo's trajectory towards the dark side, actually sets off his nephew's villainy by attacking him.
This leads Kylo straight to Snoke, but the First Order's supreme leader is no better than Kylo's relatives. Snoke reveals that he facilitated the telepathic bond between Kylo and Rey, since he didn't believe his apprentice could deliver the girl on his own. So Kylo turns on his master, again.
These terrible role models would be enough to explain Kylo's penchant for wickedness, but something even more interesting happens when Rey and Kylo annihilate Snoke and every guard in his throne room. Rather than asking Rey to join the First Order, Kylo offers to burn it all down and start anew together.
This means Kylo isn't attached to any ideology. He doesn't care that much for any of it, which suggests that he joined the First Order to stick it to his parents, who sent him away, and his mentor, who tried to kill him. His motives can't be attributed to loyalty to the First Order or any particular belief that lines up with that regime. His brand of badness appears to stem from a well of rage and pain, which he exploits to tap into awesome power.
The prequels ran into difficulties trying to rationalize Anakin Skywalker's evil arc. Anger over his poverty-stricken childhood was never convincing, and neither was the notion that he genuinely felt imperial rule was an ideal form of galactic governance. Oddly, it didn't occur to any of the writers that the dark side could be seductive enough on its own.
"The Last Jedi" gives us a glimpse into the nature of the dark side when Rey goes into the cave, sees herself multiplied by the thousands, and gets no answers about where her parents are. She feels desperately alone, and it's only when she confides in Kylo afterwards that she feels less so. When Rey gives into her desire not to be alone, she ends up teaming up with Kylo to fight off Snoke's guards, maybe because she feels more powerful when she's with him.
She's not, of course. Just as Kylo is actually more potent when he's not trying to please Snoke, Rey can achieve power independently. But what matters is how the dark side operates, and what Rey's vision demonstrates is that it finds it feeds on fear. So, what's Kylo afraid of?
We see that he hates disappointing his masters. He's truly heartbroken over the fact that Luke tried to kill him, and he turns on Snoke when he fesses up to his lack of faith in his young apprentice. It's also Snoke's dissatisfaction and taunting that prompts Kylo to destroy his mask. He's clearly intent on indulging his mentors, but given how mighty he is on his own, you have to wonder why.
From this, we could deduce that Rey is afraid of relying on herself because it reminds her that she's all alone, while Kylo is also afraid of relying on himself because he's not confident enough to go it alone. In both cases, their fears make them team up with destructive people they don't need. As tremendous as the dark side may be, it also seems to hold you back.
This leaves me very curious about where Kylo is headed next. Unlike Vader after "The Empire Strikes Back," whose family ties paved a clearer path towards redemption, Kylo doesn't have much to cling to at the end of "The Last Jedi." You know he's still fixated on Rey, but she made her choice, and he's not interested in turning good. Possibly because he's seen "good," and it doesn't deliver.
What "The Last Jedi" prepares us for is a rudderless Kylo taking the lead. That scenario appears to be his greatest fear, so it has the potential to take him to an even darker place.