Question

what does Mr.shiftlet's treatment of lucynell at the end reveal about his intentions all along?

Answer 1

It reveals that he conned the women. He never intended to be a good person and stay with Lucynell. All he wanted was the car. This is foreshadowed when he first sees the car. It is also shown in his behavior with Lucynell before they leave her home. 

Answer 2

Throughout the story, we learn that Mr. Shiftlet's intentions were selfish and self-centered. From the moment he had the first interaction with Lucynell and Lucynell's mother, it was clear that Mr. Shiftlet was not actually interested in Lucynell. This becomes even more obvious towards the end of the story, when he abandons Lucynell. This confirms that he was interested in the car all along, and not in helping the women.