So everybody has been saying that Kylo Ren will almost definatly surpass Darth Vader one day. I am here to tell you that this statement, is complete BS. (Major spoilers ahead, you have been warned)
While Kylo Ren does have a unique backstory, I just don't feel it with him, I just don't see the reason he embraces the dark side, Kylo Rens story is just kinda all over the place. Like he is Han and Leia's son, and he betrayed Luke sky walker, and he wants to finish what his grandfather Vader started (whatever that may be)
Now Darth Vader on the other hand killed a whole tribe of sand people showing his capability with hatred, was convinced that the only way to protect his love is by learning the new ways of the dark side of the force, destroys all stability by assaulting Courencent and killing all the Jedi, then finally attempting to kill his best friend. You see Darth Vader actually had quite a few reasons to turn to the dark side, and with the emperor whispering in his ear manipulating him, anakin was almost destined to turn to the dark side at some point.
now strength wise, if Vader and Ren were in a duel, Ren would definitely win. Vader is weak and is unable to use the force do to the suit, while Ren on the other hand is very skilled with his upgraded light saber, and can use the force rather easily.
who is more powerful. Vader. It has and always will be Vader. Vader ruled the galaxy for maybe 30 years, Kylo Ren has never become a Sith Lord yet.
so there you have it, Vader will always be superior to Kylo Ren, I mean Kylo Ren can and will become a huge bad guy and rule the Galaxy at some point, especially because it really hammered in the fact that he is evil because he killed Han Solo, one of the most beloved characters in the franchise, but he will never have such a tight grip on the Galaxy as Vader did. Let me know what you think in the comments : )