Speed Demon is Jerry McGee, an enemy of the Flash. He and his wife Tina McGee are also friends of Wally West. Originally a scientist at S.T.A.R. Labs, his mental instability and obsession with his work led to the destruction of his marriage, after which he went crazy and became bent on revenge. Developing a high-tech suit that would imbue him with super-speed through steroid usage, he became a costumed super-villain. McGee was eventually brought back to normal, and even reunited with his wife. Speed Demon was created by Mike Baron and Jackson Guice, first appearing in The Flash (Volume 2) #5 (1987).
In the Amalgam Comics Universe, Speed Demon is a legacy similar to the Flash Family combined with Ghost Rider. Jay Garrick, Blaze Allen and Wally West have all been Speed Demon. This version was created by Howard Mackie, James Felder, Salvador Larroca and Al Milgrom, first appearing in Speed Demon #1. (1996)