Jason Wynn is a crime lord and business man who killed Al Simmons, who then becomes Spawn.
Wynn made a deal with Malebolgia in which he traded the soul of Simmons in exchange for psychoplasm. The sample that he obtained was combined with Simmons' memories and transformed into a training ground made up of building of his past known as "Simonsville". Simonsville was destroyed by Spawn and Wynn was defeated, having his memory wiped and was returned to Earth two days after his disappearance.
After this, he would work on and off with the Clown to bring about the end of Spawn. When Mammon restored the Clown's existence on Earth and gave him a pass to take a new body, he chose Wynn and became a dominant role in his psyche. He then went on a killing spree in his spare time, murdering women who resembled Wanda Blake. Wynn was caught in the act, and in the Clown's face paint at a construction site. Spawn then saved the women and defeated Wynn. The Clown then let Wynn let go of the steel girder he was clinging to and fall to his death, allowing him to take full possession of his body.
Wynn then reappeared in issues 167-168, having been separated from the Clown after the white light event, but his hands have stayed permanently red. Throughout his career, Wynn has gathered incriminating information/evidence on various governments and organizations, providing him a bargaining chip to bring him back to his authority if lost and preventing him from being terminated. However, Spawn revealed that he found and destroyed all the evidence Wynn had found, allowing Wynn to be vulnerable to those who want him dead. Spawn then leaves Wynn, seeing him as a "dead man".
In the movie, he is played by Martin Sheen. He is less powerful than his comic counterpart, and is a lot more emotional and hot-tempered. He, along with his right hand Jessica Priest, killed Al Simmons in person, instead of having him killed.