The Thinker
The Thinker appeared as a judge in the 'trial' of the JSA, but was revealed as the Green Lantern in disguise, having captured the real Thinker after escaping Brain Wave. This led to the Injustice Society's defeat. Together with the Fiddler and the Shade, the Thinker was the man behind the decades-long "abduction" of Keystone City and the original Flash, after which he was defeated by the Flashes of two eras. His "suspended animation-time" in Keystone kept the Thinker young over the years, and he continued his criminal career in modern times.