Which villain created the body that became Vision?

The villain who created the body that became Vision is Ultron.

In Avengers: Age of Ultron, Ultron builds a synthetic vibranium body intended to become his ultimate physical form. The Avengers recover that body before Ultron can complete the transfer of his consciousness. Tony Stark and Bruce Banner instead upload J.A.R.V.I.S. into it, while Thor’s lightning helps activate the body and its Mind Stone.

That process creates Vision, rather than giving Ultron a new body. Vision therefore has a complicated origin: his body was designed by Ultron, his operating consciousness comes from J.A.R.V.I.S., and the Mind Stone powers the gem in his forehead. Tony Stark, Bruce Banner, Helen Cho, and Thor also contribute to his creation in different ways.

The comics have a related but different history. Comic-book Ultron created Vision as a weapon against the Avengers, using an earlier android body and brainwave patterns. The MCU simplifies and remixes that origin, but Ultron remains the villain responsible for constructing the body.