Kylo Ren, the villain you hate to love but you love him anyway. He has already made it into the hearts of many Star Wars fans, has spawned memes and parodies and is in short a firmly entrenched part of Star Wars canon and geek/pop culture now.
While he was the main active antagonist in The Force Awakens, he came across as a far more nuanced and conflicted character than any of his predecessors except for his grandfather at the very end of Return of the Jedi.
Kylo Ren also makes some remarks during The Force Awakens and acts in certain ways that makes me think he is not quite as much on the Dark Side as you might expect. I also think he is not quite on the Dark Side on purpose.
Let me elaborate:
In the first trailer already, Kylo Ren says „I will finish, what you started“
In the same scene he also asks his grandfather for help. His grandfather is Anakin Skywalker, who was Darth Vader right up to minutes before he died. Darth Vader was redeemed by Luke Skywalker and became Anakin Skywalker again who upon bodily death became one with the Force and turned into a Force Ghost can be seen clearly in this (original and unaltered) still from Return of the Jedi:
There is no way I can imagine that Kylo Ren would not have been aware of the final fate of Anakin Skywalker. Luke surely shared it at one point with Leia and either or both of them must have told Ben Organa-Solo / Kylo Ren at some later occasion.
Also, it has to be noted that it was Anakin Skywalker, not Darth Vader, who sired Luke and Leia.
Anakin Skywalker was, believed to be the one chosen to destroy the Sith and bring balance to the Force, see this clip:
Again: „I will finish, what you started“
Anakin Skywalker (redeemed) actually destroyed the Sith by killing the last Sith, Darth Sidious. He managed to fulfill one part of the prophecy concerning „The Chosen One“ but he did not manage to bring balance to the Force. Kylo Ren has set out to achieve this. If he would truely be on the path to the Dark Side, why would he ask his redeemed grandfather for help who became a force ghost and joined Master Yoda and his teacher Obi Wan Kenobi? It only makes sense if he wants guidance to bring balance to the Force. Also, Kylo Ren is not a Sith, he is a Knight of Ren (from what we know now, anyway). The Sith are still destroyed.
Further, I am under the impression he has still more Light Side in him than he wants to. He has to become darker to be balanced. This is why he killed his father, but later sucks when he fights Rey. He needed to kill Han Solo to get closer to the Dark Side but never wanted to kill unless it is necessary for his plan.I think he does not really want to kill Rey, because he realises she is his „emergency off-switch“. Should he fail and be consumed by the Dark Side, she will still be capable of stopping him. Alternatively, he could see her as a deciple for later. She is a Force user and has shown both noble heroism and rage. She is not a Jedi yet. She could still become a balance Force user, capable of weilding both sides.
It is also noteworthy that Kylo does not Force-choke people who failed him and his rages seem almost comical. He is not that evil and has to act out his rages forcefully in order to become properly enraged as one would expect from someone strong in the Dark Side. There is still more good in Kylo than is good for his plan.
If this is all true, why was he looking for Luke? I guess it was not to kill him. I speculate he wanted to win him over andor capture him in order to share some insights he gained from the Dark Side, also, let him in on his plan and maybe team up with him in order to kill Snoke. Or he simply wanted to check wether Luke was dead or not. Maybe his plan was to first kill Luke and then Snoke, leaving only him, the only one remaining with training in the Light and the Dark Side. Here opens another venue of speculation: Maybe Rey’s entry messed up Kylo’s plan because he did not factor in another Force user who would oppose him. Maybe this will be a major driver in the upcoming movies.
So, I think Kylo Ren is a double agent, not for the Jedi, but for his own agenda, which is to bring balance to The Force.