Ren is awful. You want to make a conflicted dark sider? Ok great, I mean Vader was that technically, but I get the concept. But Kylo is a massive failure of telling not showing. You want to show him struggling against the light? Have him spare people in the village in the opening, or hesitate greatly before giving the order. Have him actually hurt Rey a bit, and feel bad about it. Show him uneasy about blowing up billions of people. Make us think that he is THIS close to turning to the light, then pull the carpet out from under us. Then the scene with Han would work.
As it stands he acts like a mopey teenager, who might as well have posters to The Space Cure in his bedroom, as he talks about his pain and not wanting to be drawn into the light to what's essentially a skull. Hell, he's so much a a mopey teenager stereotype that people actually don't realize the dude is supposed to be 30 damned years old. He ceases to be threatening at all by the end of the film. It would honestly not bee too bad if Ren was the protagonist. And who knows, maybe there is a double bait and swtich, and he will eventually be the one on the heroes journey, but I find that doubtful. This isn't "The Emo Awakens" after all.
With the exception of movie Grievous. every single villain in the TV shows or movies is better than Kylo Ren. Hell, Hondo Onaka is more threatening and effective than anyone in the First Order, and he's comic relief. Compare the three villains in Rogue One to the three villains in TFA, and tell me who is scarier.