Right after Kallen has liberated Lelouch from Pendragon, as she's flying back to the Ikaruga on the Gawain. She notices how peaceful he looks and just how much stress he has to carry as Zero. In a weird way it gave this troper a strong WAFF.
Almost all of Kallen's interactions with Lelouch in general. The strength of their relationship, even eight years after their separation, only seems to have grown instead of deteriorating. To the point that Lelouch outright admits to her that other than C.C., she is the only person in the Black Knights he completely trusts. Enough to trust her with his back, both to protect him and to take him down should he ever fall from the right path.
The fact that it is Kallen's life being in danger that persuades Lelouch to take up the helm of Zero once again.
When Kallen expresses uncertainty in her ability to live up to Lelouch's expectations, he responds that he knows she can because he chose her to be his Knight of Zero. This unshakeable faith in her abilities spurs Kallen's Heroic Second Wind and lets her defeat the Wyvern in a Crowning Moment of Awesome.
He may be insane, an extremist, and even more hypocritical than before, but Suzaku still wearing the Knight pendant Euphemia gave him is touching, in a depressingway.
Tohdoh, while reminiscing on his father, remembers how harsh their argument over his decision to become a soldier was, and how it was the last time either of them spoke. He wonders out loud whether his father would be disappointed in him. Senba overhears this and tells him that he'd been keeping in touch with Tohdoh's father, updating him on how his son was doing, and that the last thing he heard from him was that while he still didn't agree with the path he chose, he was incredibly proud of the man his son had become.