Fred is a complete contrast to Scrooge
1. Fred arrives in Scrooge's offices "all in a glow" and "his eyes sparkled" - this emphasises the warmth and friendliness of his character. He's the opposite of Scrooge, who's associated with the cold
2. Fred disagrees with Scrooge's miserly values. He thinks that Scrooge's wealth is useless because "he don't do any good with it" - suggesting that, unlike Scrooge, he values happiness more than money
3. He's empathetic - he's "heartily sorry" for the Cratchit family after Tim dies, even though he barely knows them. This contrasts with Scrooge, who begins the novel as a self-centred person who doesn't care about others
4. Dickens uses Fred as a foil to Scrooge's character. The differences between them emphasise Scrooge's negative qualities