Scott apologising to Kim, basically for being himself, at the end of Volume 5. Kim's reply is a completely sincere "Apology accepted", actually smiling for a change.
Scott finally telling Ramona he loves her in volume 4.
And her saying she loves him too afterwards.
Near the beginning of Volume 6: "K-Kitty."
Ramona reappearing to Scott after months of absence in volume 6 and trying to apologise to him for being such a sucky girlfriend, but she can't get it out because Scott just won't stop kissing her.
Scott: Damn it, Ramona! I forgive you already!
In volume 5, Ramona, Scott and Kim get smashed at a party, lay around in a pile on a bed upstairs and drunkenly pal around. Then when they finally leave, Kim pulls them both into a group hug before heading home.
Kim: I seriously wish I could...like...be you, Ramona. I mean, you're so...y'know?
Ramona: *kisses Kim on the head*
Though it doesn't make Scott feel much better, there's something very sweet about Knives telling him in volume 6 that even though she's moved on, she still cares about him.