The Vision didn't get off on the right heroic foot as a matter of fact when he first encountered The Avengers he was an enemy not a friend. In the course of demonstrating his powers including super strength, and the ability to vary the density of his body. The Vision revealed that he had been programmed by his creator to destroy [The Avengers](movie:9040), his creator was Ultron 5 who had recently fought the Avenger as well. Fortunately the Vision rebelled against Ultron 5 and defeated him, thus earning the trust, and respect of the Avengers.
Back at Avengers headquarters the Vision was encouraged to dig deeper into his memories and try to remember to try to recover details of his creation. He succeeded and recalled the moment when he was brought into existence by Ultron 5. The android also recalled that he was filled with curiosity far than what was appropriate for a simple machine. As the Vision related his tale Goliath realized that the androids solar power design had more similarity with that of a synthezoid a failed experiment that he himself had abandoned sometime ago.
Goliath soon realized that the synthezoid he had created had evolved into Ultron 5. He also learned that Ultron 5 had stolen the brain patterns of the superhero known as Wonder Man, and implanted his conscience into the Vision. It was this addition of Wonder Man's consciousness that accounted the Vision's strong will, heroic nature, and ability to experience emotions. Over the years there have been modification to the Vision's origin, the most significant involves the creation of the Vision's physical body.
It was revealed that Ultron 5 did not actually create the Vision;s android shell, rather he kidnapped the body of the original Human Torch. This character created in the 1940's had the same powers as the a Human Torch of the Fantastic Four, however as the modern Human Torch is human the original Human Torch was an android. Ultron 5 forced the Human Torch's original creator to alter the face of his creation back to synthetic life, there he then reprogrammed him to do his biding and added Wonder Man's brain patterns. In the year since his debut in 1968 the Vision has undergone a lot of changes some of them drastic.