The battle is in New York City, morals are off. No speed-blitzing, and no BFR. Fight is to the death. All characters are at full power, in their most current incarnation.
The Authority Members:
Jack Hawksmoor: http://dc.wikia.com/wiki/Jack_Hawksmoor
The Engineer: http://dc.wikia.com/wiki/Angela_Spica_(Earth-50)
The Justice League Members:
Green Lantern (Hal Jordan)