Disclaimer: If I owned Star Wars, I would've asked Haiden Christiansen to be less creepy in the prequels.
Looking back, there was a split second where Kylo Ren had considered not skewering his father. Filled with honest despair and uncertainty, he had almost turned the deadly sword in upon himself. He was still uncertain when Han Solo had called out his name, his former name. Memories of good times with his family had bubbled up from under the bitterness he thought he'd buried them in, and he'd felt his eyes burn beneath the mask. The anguish in his father's shout was a double-edged sword, and although he knew that he should only feel sparking irritation, part of him grasped onto that single syllable with desperate yearning.
He wasn't lying when he'd told Han that he felt conflicted; in fact, he still wouldn't be lying if he said the same thing now. Every look back, every meditation upon and reexamination of that moment tore him apart inside. Even after his master had praised him extensively on the well-played deception of his move, the pure malice that he claimed had to have driven the act, Kyo Ren still couldn't settle. Every shred of his mind, of his thoughts, his memories, his emotions, everything was at war. Nothing had been able to settle him down since that moment, since that instant of push and pull.
When the raging currents of his rawest emotions had exposed themselves in the trembling of his hands and Han had taken his saber, his hands, to help him, to help him, his mind had imploded. It had collapsed inward and devoured itself. He had never felt so empty as in that moment. Every malicious thought he'd ever had about his father was wrong. The Force had flowed out of him like air out of a balloon, leaving him small, helpless, indecisive, floundering. At first he had wanted to die. The instant Han had placed his hands on his saber, the urge to commit suicide had overwhelmed him, and he had weakly attempted to pull the blade back towards him, but his father's hands remained firm. There was no way his father was going to let him kill himself, and Han had begun to steadily pull the saber away from him by the time this fact finally registered.
"Anything." What a hypocritical fool!
Frustration, irrational though it was, exploded through him. His once empty soul was flooded, filled to the brim with a bitter, childish frustration that his father, Han, had once again interfered with him. He had no right! After all the times he had run off, abandoning him and his mother, he had absolutely no right to think that he could still tell his son 'No,' to think that he could march up to him, a man he never bothered to know, even as a young child, and act like he knew what he wanted, what was best for him. Kylo Ren had pulled his gaze up to Han's, stony-faced, and before he knew it the button was already pushed.
The red light had illuminated his father's grizzled face. His expression had trembled, a screen of disbelief flickered over heartbreak and regret. The corners of his mouth had twitched, and Ben, Ben Solo, had leaned into the touch of his father's fingers, instinct and apology blended into the gesture, but then Kylo Ren had taken over, taking a step towards Han to push his arms away, and the body had tilted heavily over the railing before sliding off into the abyss.
Ben had wanted to scream loud enough to be heard in space, to cry until the lakes of Naboo dried up to nothing, to tear his hair out, to despair, to beat against the railing and the cat walk and tear apart that accursed base with nothing but his grief and his saber, and Ben still did; every day and every night, Ben still did.