I think we see the most outward reaction by Scrooge to the final ghost. However, I also think that the Ghost of Christmas Past may have touched one of the biggest nerves with Scrooge - that of his time spent with Belle, and how he ended up losing her because of his ambition for wealth. When the ghost shows Scrooge the time that Belle broke off their engagement, Scrooge is very upset:
'"Spirit!" said Scrooge, "show me no more! Conduct me home. Why do you delight to torture me?"'
After the ghost takes Scrooge to see Belle with her husband and children, Scrooge then says, "Leave me! Take me back! Haunt me no longer!"
I think Scrooge reacted quite strongly to the visions shown by this Ghost of Christmas Past, and that the emotion and agony he demonstrates with the Ghost of Christmas Yet To Come is the culmination of all the horrors he has been shown that night.
Every time I read this book I ask myself the same question. I believe that all of the ghosts affect Scrooge equally in some ways; however, I, too, believe that the Ghost of Christmases Yet to Come has greatest impact upon him in the end.
There's a fairly straightforward answer to this question, and a somewhat more complicated one. The straightforward answer is, the Ghost of Christmas Yet To Come had the most effect on Scrooge. Of the four spirits and the visions they showed him, this one spurred him most directly to change. Right after that visit he began to share his fortune with those in his life.
The somewhat more complicated answer is that you could make a case for Marley's ghost having the most impact, because Marley and Scrooge had shared their lives and Marley opened the way for the other ghosts.
I think Ghost of Christmas Yet To Come had the most impact on Scrooge, but I believe Scrooge was more shocked with the ghost of Marley.
If was the Ghost of Christmas Yet to Come that had a direct impact to Scooge's life and actions. When he heard that he was going to die, he fell to his knees and begged for a second chance to change into a better self. His whole personality changes after the encounter with the spirits, he becomes more charitable. He told a boy to go to the poultry shop and bring the big prize-winning turkey to him, which he would send anonymously to the Cratchits. He becomes more tolerant, supported by the fact that he had forgave Bob Cratchit for turning to work late, unlike his usual behavior, and even suggested to increase his salary.
In my opinion the third spirit as the more more effect on scrooge,than the another two spirts bacthe first one show hm howa he used to be, and the second one show him what's around him ,but before the third spirt scrooge may not change him self, but after he saw how it will end ( people laughing at him and saling his things no one care about him, no one care that he has died)things change he did not want it to end like that so he changed himself in order not to end this ouful end