Secret Origins (1986 DC 2nd Series) #32
Cover art by Eric Shanower. The Secret Origin of the Justice League of America, script by Keith Giffen (plot), Peter David (dialogue), and Gardner Fox (story), art by Eric Shanower
When contenders for the leadership of Appellax stage their combat on Earth through "battle form" surrogates, the Martian Manhunter, Aquaman, Black Canary, the Flash, and Green Lantern first encounter and defeat the first 5 individual battle forms separately, but have to work together to defeat the sixth one.