Lorna. After Sonya's death she became even angrier and her wishes for revenge were even more fierce. Yes, John had a moment of grief, but I think it ended too soon and just a couple episodes after he was kissing Clarice.

After Lorna, I would say Andy, another one who also become angrier for that reason after watching Sonya's murder.

^ I agree with a lot of the things you said, but I also kinda felt like Lorna was much less affected than I expected her to be.

Lauren is very affected too, she talks about it constantly, it's like she can't stop blaming herself and feel bad about it.

It changed Andy too, affected him a lot, he doesn't talk about it like Lauren but it's clear, it's one of the reasons why he decided to go Team Hellfire. There's a conversation with Lauren and Andy where they talk about her death; Lauren: "It affected me too" Andy: "Affected you how? You've acted like nothing's changed"

I considered John at first, but then thought "No, he got over it so fast"

It clearly affected Clarice too, but not nearly as much as Lorna, Lauren and Andy, all those three have been affected for a long time.

This is a hard question! But I'm gonna go with Andy

But like you guys said they were all affected a lot by her death, but Andy, Lauren and Lorna never got over it like John and Clarice did and for Andy and Lorna it hurt them so bad that they would no longer play a victim "because" of her death partly, at least it was what motivated them, to stand up and fight now.

She was like the only character actually talking about it for a while