Final answer:
Attitude is the most relevant internal psychological process associated with the post-purchase evaluation stage of the consumer decision-making process.
Step-by-step explanation:
The most relevant internal psychological process associated with the post purchase evaluation stage of the consumer decision-making process is attitude. Attitude is our evaluation or feeling towards a person, idea, or object, and it plays a crucial role in the post-purchase evaluation. After making a purchase, consumers evaluate their overall satisfaction with the product or service based on their attitude towards it.