Justin was the first person mentioned/ blamed for Hannah's suicide. Hannah said, "A rumor based on a kiss started a reputation that other people believed in and reacted to."(30) Because Justin told a couple people about a kiss, the information got twisted and snowballed out of control. Arguably that is what started it all for Hannah. Justin can't take back what he did. He is responsible for spreading rumors that led into much bigger problems than he could have ever imagined.
Courtney Crimsen was one of the first people to befriend Hannah Baker at her new school. Hannah says, "Was I disappointed when you said good-bye to me, Courtney? Not much. It's hard to be disappointed when what you expected turns out to be true." (110) Courtney and Hannah had a rough friendship which, in turn, ruined the way Hannah perceived girls in her grade. Because Courtney just used Hannah, she has to deal with the repercussions that come with that. Courtney chose to end the friendship with Hannah whether it was the right or wrong choice.
I predict that the final solution will be everyone on the tapes figuring out why they hurt Hannah and what their specific actions did to her. It's already know that she kills herself so there isn't much of a solution, but everyone responsible will now know the full story of how actions have consequences no matter what. Moral of the story is think before you do something because you never know what consequences your actions will have or cause.