This is a great question and I am sure that there will be many differences of opinion. Already there are two opinions. In my view of things, the most visible turning point comes when Scrooge begins to connect with tiny Tim. When the second ghost brings Scrooge to the home of the Bob Cratchit and he sees the love and generosity, even in view of their poverty, his worldview is challenged. In other words, he begins to have a softer heart. This is evidenced in his concern for tiny Tim. He even begs the ghost to tell him whether Tim will survive. This fact alone shows that he is no longer only interested in himself.
When the ghost replies that there will most likely be an empty chair at next years dinner, this fact begins to hit Scrooge. The reader is given hope that Scrooge can be redeemed and by the end of the story he is. It is clearly seen in his "adoption" of tiny Tim.
The turning point in Dickens classic A Christmas Carol comes during a time of deep emotional crisis that is experienced by the main character (Scrooge) as the ghost of Christmas Present is providing escort. The realization by Scrooge that he is pititied and or despised by others instead of the respect he sought begins the softening of his heart. As the ghost of Christmas Present escort continues Scrooge comes to realize that life is not about what you have instead it is what you do for others.
when the ghost of christmas futre comes to haunt him and he sees no one pitties his death