The time when Data-Sora said "thank you" to Data-Naminé, just like the real Sora promised the real Naminé. The fact that Data-Sora is the one to do it and not the real one doesn't make it any less poignant.
"Rest easy. Your hurt can be mine now."
Coded and Blank points. Just knowing that those who've fallen haven't been abandoned, least of all by Sora.
When Data-Roxas merges with Data-Sora, the latter feels the former's pain. His response?
Data-Sora:Rest easy... Your hurt can be mine now.
Any scene with Donald and Goofy working together with Data-Sora. It's just been so long since the last time they were a trio, and even they know it.
Mickey reveals he was in Traverse Town when Sora originaly arrived there. Pluto hears a whistle — the whistle of his master — and dives into a portal of Darkness after him. Talk about loyalty to your master — Pluto doesn't know what is inside this portal, or what it will do to him, but he still does it.