LogFAQs > #976750615

PA thing worth noting too, regardless of which variant of the DC guys we use, is that... well, lets use DCAU as an example with Flash and Supes. Supes at one point "stops holding back" against Darkseid and starts hitting hard enough and moving fast enough that he could probably easily overcome the physical FF members. And flash at one point goes running around the world multiple times a second (at basically the cost of his existence) during that finale where he is fighting the combined darkseid-brainiac (though it ends up being Lex who seemingly finishes him off).

Point is though, that they never use anywhere near this power from the start. Its more of a "reveal" moment when its like "okay, you guys are strong, I need to actually stop pretending like everything in the world is made of paper and eggshells to me, and let loose." So if the Justice League, especially an lower power version of them, is fighting normally, those endgame feats may simply never happen due to Flash and Supes getting turned to stone or stopped in time (Flash may actually have resistance to that one) before realizing they need to go nuts.