Karenin forgiving Anna and Vronsky, and bonding with their baby. This makes it all the more touching when, in spite of society's disdain, he decides to adopt the orphaned little girl in the end.
The 2012 adaptation ups this with the ending. Karenin sits in the field, with mild bitterness. He he cannot help but to smile at Seyozcha and little Anya playing together.
Levin's second proposal to Kitty, their wedding, the birth of their child ... pretty much any scene they're in.
In the 2012 adaptation, when Ana goes to a play, it becomes apparent that everyone is shunning her because it's become public knowledge that she's having an affair. Princess Myagkaya continues to talk to her as if nothing's happening, and just before the scene freezes with everyone staring at Ana, Myagkaya squeezes her hand reassuringly.