"Turns out I'm really good at making weapons." There is some bitterness in that tone but it's all at himself. He learned a lot of bad things about himself during that fight, including that he's incredible at designing and creating violence. It is not something anyone would want to know, let alone Jayce.

"Back home I ... I meant to tell you but things kept happening." They were always busy or she was adjusting or they were kidnapped away on a ship. "I waited too long to tell Viktor and it almost broke us up, as friends. I don't know if he'll ever forgive me." This was before their relationship. It required Viktor to forgive him before they could move on together.

"I made a Hextech weapon, a hammer. Your friend from the Undercity, Vi, she asked me to help her take on Silco off the record." To get around the Council who she knows refused either of them the ability to attack. But Caitlyn probably saw how angry he was, how desperately he wanted to do something. It didn't take much. "We destroyed a Shimmer factory. People died." They killed them. "He wanted me to promise I'd never do that again."

Make weapons. Choose violence. Jayce feels enormous guilt over what happened, it made him spend many months completely wrapped up in self-hate, in disgust at himself. Despite coming off as arrogant, he has a lower self-esteem than it seems, so it was easy to hate himself. He's come to the other side of this as a learner.

"I need you to ...." He sighs and holds her hand. "I'm telling you because he's afraid if I lose him, I'd go down a dark path." And Jayce hasn't exactly dissuaded him. He just doesn't know what to do with all of this pain. His anger has never been safe to go anywhere either. "I don't want that either."