There's more goodness in this Tiny Tim alone than in all Scrooges of the universe. He even thanks Scrooge for his Christmas dinner in the Ghost of Christmas Present sequence, which is a canary so small than it would not feed this adaptation's Ghost of Christmas Past (Jiminy Cricket).
Scrooge seemingly playing his rudest side and threatening his employee for the worst... before revealing a bag of toys and kindly granting Cratchit a raise and a promotion. And the short ends with him rocking all the children in a rocking chair.
The way Scrooge can barely contain his laughter while still pretending to be a jerkass. He's really enjoying himself in this scene, which makes his redemption feel all the more genuine.