Final answer:
Rembrandt stands out among his contemporaries because he often created multiple states of a single image, experimented with ways to improve and extend the expressive power of his images, and painted numerous self-portraits.
Step-by-step explanation:
One reason why Rembrandt stands out among his contemporaries is because he often created multiple states of a single image. Rembrandt was known for experimenting with different techniques and methods to improve and extend the expressive power of his images. Additionally, he was famous for his self-portraits, creating over eighty unique portrayals of himself throughout his life. His self-portraits not only showcased his artistic skills but also provided insight into his personal development and psychological make-up.