I don't own Charmed nor will I ever. No copyright infringement intended.
Chris dying and fading away in his arms signalled the death knell for everything Leo believed in since he became a Whitelighter. In that moment, the grief and anger caused something inside him to fracture that he was never able to repair. And it sent him down a path of no return that nobody had quite expected. Hunting down demons helped for a little bit but the fury refused to dissipate. Unfortunately, this meant the Avatars were able to manipulate him at his lowest and most vulnerable. Piper confronted him right before his vision quest because enough was enough and she wanted her husband back. "You can't keep doing this to yourself, Leo. It's not healthy. You're not a danger to anybody so I wish you'd stop thinking that."
"I don't want to hurt you or the boys," he admitted. It was his worst fear and something that had been in the back of his mind since he and Penny got into before Chris' Wiccaning.
"You're not going to hurt us. You're such a sweet man who's just lost his way. That's all," she comforted. Her heart broke for her clearly distressed husband.
Piper picked up Chris from the playpen and handed him to Leo. "Hi, buddy," he whispered, wishing he could stop seeing the adult version he had failed so badly.
"Just talk to him. Get it off your chest before the vision quest," Piper encouraged. She kissed both of them and headed upstairs to check on Wyatt.
Leo headed to the conservatory but instead of sitting on the couch, he sat down on the floor and stared at his youngest. Chris cooed at him and he wished once more that he hadn't broken his promise to his son. "Mommy thinks it'll help if I talk to you but I don't know if it will." Tears started to splash down his face. "I don't know if I can trust the Elders anymore. It's pretty complicated and a long story, kiddo, but I want you to know that I won't let anything happen to you or your brother. I've lost my way and I don't know if I can ever find it again. Mommy thinks I can but I just don't think it's possible. Your adult self dying broke me in so many different ways that it's really not possible to fix me. And I'm going to try to be a better dad to you this time because that's what you deserve. And I didn't get a chance to tell him this but I want you to know how much I love you." Tears continued dripping down his face as he vented to the baby who didn't understand him.
Piper stood still around the corner and sobbed - for the pain and grief Leo was experiencing and because of her own grief.
Becoming an Avatar flipped some sort of switch in Leo but the grief lingered in the back of his mind. He never fully healed and it stuck around, waiting until the perfect opportunity to strike. Unfortunately, it chose to sneak up on Leo shortly after he became mortal again. Watching TV when it happened, he suddenly remembered a movie he and Phoebe had forced him to sit down through just to relax one night (it hadn't worked but at least they had tried and Chris had enjoyed himself). Unfortunately, he happened to be flipping through the channels and landed on the exact movie they had watched that night. The grief rose up like a tidal wave and he turned off the TV, sitting frozen on the couch. Piper walked in to join him and knew instantly that something was wrong. "Leo? Please talk to me," she begged.
He turned towards her and the clear pain in his eyes nearly took her breath away. "I miss him, Piper. And I know we still have Chris, that we didn't really lose him, but fuck, I can't stop thinking about him. He didn't deserve to die."
"No, he didn't. And I'm sorry it came at the hands of someone you trusted and we cared about." Piper knew that was one of his biggest problems with this. He felt responsible for letting Gideon into their lives.
Leo broke down then and only protested a little when Piper pulled him into her arms to comfort him. He needed her support much more than he was willing to admit.
It wasn't until Chris' memories of the other timeline - his trip to the past included - returned that things came to a head. Leo's guilt over the situation reared its ugly head again but he tried to ignore it and be happy that his son remembered everything (even though Leo hated that it meant all the bad too). Chris was curious about why his father decided to fall from grace and asked his father about it. "It's weirding me out a little that you're older now even though I'm used to it." Chris was confusing even himself now so he wasn't sure how everybody else was keeping up with him.
Leo snorted. "Yeah." He looked down at the floor and then back up at his middle child. Suddenly feeling self-conscience, he had to take a few minutes to compose himself. "After Gideon killed you, I lost all faith in the Elders. It was the death knell for my belief in them. I trust the Elders now, of course, but not like I used to. Becoming mortal was one of the best decisions I ever made and I don't regret a thing."
"Wow." Chris really didn't know what to say to that, unsure of how to react to the revelation that his death had torn apart his father so badly. It was difficult to comprehend. "You do realize, though, that it was Gideon's fault right? It was never yours."
Leo didn't want to correct his son so he said nothing. "I'm just glad you have a better life now, Chris."
"And neither one of us gave up so that's really all that matters. We got this, Dad." Chris winked at him. Leo laughed and hugged his son.
Chris' death would haunt Leo for the rest of his life even though his son had assured him he wasn't at fault. It stuck to him like glue and refused to let go although the grief lessened over time.