AU where Snoke's influence, the frustrations and insecurities that came from his family, his own deeds have all taken a toll on Ben's mind, until it snaps when he is tasked with killing the young padawans.
He is still powerful, but his mind is in pieces. He only makes sense half the time, his mood swings are off the charts. It suits Snoke just fine though, since he still has the attack dog he wanted.

Until the bridge scene, where Han confronts his son and realizes the extent of the damage Snoke did to him. And Ben is more torn appart than ever, because in his broken mind he can't even tell if he wants to stay with Snoke or go home.

Optional:
+ Ben does go home. Things don't immediately get better, but he is being taken care of and there is progress. Ben/Poe would be lovely too.
+ Kylo/Hux, with Hux taking advantage of Ben's madness to make him rely on him.