Scrooge's Heel–Face Turn, especially his reconciling with Fred, who welcomes him in open arms. Janet is cynical but still gracious. When he tells her "I was in love once. Can you believe that?" and Janet sincerely answers "yes".
Scrooge apologizing to the solicitors, and giving a very generous donation, so generous that the two can't hide their excitement.
The last fifteen to twenty minutes are one long crowning moment of heartwarming.
The final image of a now-healthy Tiny Tim running to Scrooge, who picks him up and kisses him, and the two of them walking down the street together. It's virtually the same as the finale of the 1951 Alistair Sim version, but every bit as heartwarming here. Possibly even more so, since this Scrooge has a Kick the Dog moment toward Tiny Tim near the beginning that Sim's doesn't have, making his ultimate loving relationship with him even more striking.
A small, related moment that comes earlier: Scrooge does not ask the Spirit of Christmas Present whether Tim will walk unaided but only whether he'll live. This reinforces he cares for Tim as a person and not simply an ill to be cured. The fact that Tim not only lives but does walk unaided in the end just makes the ending all the sweeter.